GASTROPODS: TROCHIDAE TO TURRITELLIDAE


sinus very shallow and wide, the apex just above carina; growth-line angle very wide.
 Height (incomplete, 4 whorls) 39 mm, diameter 23 mm (largest figured specimen).
 Type: Johns Hopkins University.
 Type locality: Zorritos, Perd, Zorritos formation (early Miocene).
 Turritella abrupt occurs in the middle part of the Gatun formation, but is rare. It is represented by the figured specimen of moderate size, collected in the eastern area, and by very small specimens from the western area. Adhering calcareous sandstone somewhat masks the strength and sharpness of the carina on the largest figured specimen.
 This overnamed Turritella, which reaches a relatively gigantic size (height about 200 mm), is found in Perd, Ecuador, the Darien basin of Panama, the Chiriqui area of Panamni, Colombia, and Venezuela, generally in formations of middle Miocene age. In Peru', however, it occurs both in the upper Zorritos and Cardalitos formations, dated as late early and middle Miocene, respectively, by Olsson (1932, fig. 2, p. 42). The occurrence of T. abrupta in the Miocene of the Isthmus of Tehuantepec (Woodring, 1928, pp. 66, 98) cannot be confirmed at the present time. The fossils on which that record was based have been mislaid or were misidentified.
 On the basis of the characters of intermediate and late whorls, T. abrupta may be considered a large very strongly and sharply marinate subspecies of T. ocoyana Conrad, of the middle Miocene of California. Nevertheless these two forms show a considerable difference in development of sculpture. According to Merriam's (1941, pl. 31, fig. 1) illustration of the early whorls of T. ocoyana, fairly strong spirals, other than the middle and anterior spiral, appear at an early stage. On the early whorls of the Gatun specimens of T. abrupta such spirals are weaker and appear at a later stage. Until additional data on the sculpture of the early whorls are available, specific rank is retained for T. abrupta.
 T. trinitaria Maury (1925, p. 230, pl. 42, fig. 10; Vokes, 1938, p. 26, fig. 29; Rutsch, 1942, p. 129), from the late Miocene Springvale formation of Trinidad, presumably is a less strongly carinate subspecies of T. abrupta. T. abrupta triaitaria and T. matarucana, representing different lineages, are the last survivors of the T. ocoyana group in the Caribbean and nearby areas.
 T. ocoyana is widespread in the middle Miocene of California, but has no predecessors there. The inference that it is a migrant from tropical America is justified, for there are earlier closely related species in that region.


 Occurrence: Middle part of Gatun formation (middle Miocene), eastern area, locality 144a; western area, localities 161c, 161d, 170a. Upper part of Zorritos formation (early Miocene) and Cardalitos formation (middle Miocene), Peru'. Progreso formation (middle Miocene), Ecuador. Middle Miocene, Darien area, Panama. Middle Miocene, Chiriqui area, Panama. Middle Miocene, Bolivar, Colombia. Miocene, Falc6n, Venezuela.
 Turritella matarucana Hodson
 Plate 22, figures 11, 12
 Turritella natarucana Hodson, Bull. Ass. Paleontology, v. 11,
 no. 45, p. 31, pl. 20, fig. 4, p1. 21, figs. 1, 9, 1926 (Miocene,
 venezuela).
 Turritella plebeian A-L-Owensi Hodson, idems, p. 31, pl. 20, figs.
 1, 2, 5, 6, pl. 23, fig. 2, p1. 28, fig. 1, 1926 (Miocene, Venezuela).
 Moderately large, early whorls rapidly enlarging, late whorls slowly enlarging. Intermediate whorls moderately convex, late whorls slightly convex. Late whorls narrowly beveled at posterior suture. Sculpture consisting of numerous closely spaced spirals some of which are narrower and more closely spaced than others. Earliest preserved whorls sculptured with two spirals: one at middle of whorl, the other halfway between it and anterior suture. Base sculptured with very weak spirals disappearing toward columellar lip. Growth-line sinus very wide and shallow; growth-line angle very wide.
 Height (incomplete, 5 whorls) 44.5 mm, diameter 16 mm (larger figured specimen).
 Type: Paleontological Research Institution, Ithaca, N. Y.
 Type locality: Locality 197, Rio Mataruca, Buena Vista anticline, near La Vela, District of Colina, Falcon, Venezuela, La Vela formation (late Miocene).
 Turritella plebeia aloeensi, also from the Miocene of Falcon, Venezuela, was based on specimens that have moderately inflated whorls. They are similar to T. matarucana in sculptural pattern and growth line, and evidently represent a form of that species having moderately inflated whorls even at a late stage.
 Despite the absence of a carina and the presence of numerous closely spaced spirals, T. 7atarucana is allied to T. abrupta and other species of the T. ocoyana group, according to the sculpture of the early whorls and the growth line. In whorl profile and sculpture it more closely resembles the larger, more rapidly enlarging, and more convex-whorled Miocene European species T. terebralis Lamarck, which has similar early sculpture and growth line. The whorl profile and 3 Though "the original orthography of a name Is to be preserved unless an error of transcription, a lOpsus calami, or a typographical error is evident" (International Rules of Zoological Nomencalture, Article 19), a name like "A-L-Owensi" is so objectionable tnat alteration to "alowensi" appears to be Justified.


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