64 STUDIES IN GEOLOGY, No. 3 



Turritella gothica Grzybowski, Neues Jahrb. f. Min., etc., Beil. 

 Bd. 12, p. 645, pi. 20, fig. 10, 1899. 



"Shell turreted, slender, whorls twelve to sixteen, flat or 

 slightly concave, except the body whorl, which is regularly 

 convex; whorls bordered on each side by a strong obtuse 

 ridge. Intermediate spaces ornamented by fine, raised, 

 nearly equidistant, revolving lines, about ten in the space 

 of five millimeters. Sutures small and narrow x x x. Body 

 whorl somewhat convex, except in young shells; strongly 

 wrinkled by the lines of growth, which, on well-preserved 

 specimens, are strong and acute. Base of this whorl marked 

 by from seven to ten -lines, nearly as strong as the ridges of 

 the upper whorls. Aperture rounded; outer lip thin and 

 slightly produced below." Nelson, 1870. 



The ridges or shoulders at the sutural extremities of the 

 whorl set off the suture very clearly, giving the appearance 

 of lips. The posterior rib is distinctly stronger, and tends 

 sometimes to lap over the base of the preceding whorl, giving 

 the spire a slightly step-like surface. Length of anterior 

 fragment of middle-sized individual bearing 7 whorls, 61.5 

 mm. ; diameter of the body whorl, 18 mm. Diameter of the 

 body whorl of a larger specimen, 20.5 mm. Estimated 

 length of a full-grown shell, 88 mm. 



Grzybowski's figure is that of a form somewhat more 

 squat than that apparently typical of the species, but the 

 essential characters of T. bifastigata are plainly enough 

 evident to make certain the synonymy of his gothica. In the 

 local fauna, T. alturana is most similar, but differs in being 

 much larger, stouter, and in lacking the ridges bordering 

 the sutures. Grzybowski mentioned T. cathedralis Brongni- 

 art 60 from the Lower Miocene of Europe, as similar, but 

 reference to Sacco's figure will show that the sculpture of 

 all varieties of cathedralis is far coarser, and that the pos- 

 terior ridge or lip is far more obtuse. 



Sacco, Piemonte, pte. 19, p. 31, pi. 3, figs. 12-24, inc., 1895. 



