36 PROCEEDINGS OF THE ACADEMY OF [Feb., 



This is T. exoleta Linn, of Gabb's Geology of Santo Domingo, 

 p. 240. 



Differs from T. megalohasis by having the early whorls more 

 elaborately sculptured than the later, not smoother, as in megalohasis. 

 It also tapers more gradually. Fig. la was inadvertently inverted. 



With the preceding species in the Gabb collection there is one 

 specimen probably referable to T. megalohasis, from which it differs 

 only by having the same microscopic sculpture described for T. do- 

 mingensis, and which is not visible on the small specimens of megalo- 

 hasis at hand. It tapers much more rapidly than T. domingensis. 

 Part of a whorl is shown magnified in PI. 5, fig. 14 (the figure in- 

 verted) . 



Turritella tornata Guppy. 



TurrUeUa tornata Guppy, Quarterly Journal of the Geological Society of 

 London, vol. XXII, 1866, p. 580, PL 26, fig. 12 (Cumana, Venezuela, 

 type loc). 



The Colombian specimens are all fragmentary, but have the 

 typical shape and sculpture. -The largest piece, of slightly over 

 3 whorls, measures 20 mm. in basal diameter, 41 mm. long. 



This species was also taken by W. M. Gabb in Santo Domingo, 

 the specimens smaller, and varying some in sculpture. An ancestral 

 form of T. perattenuata was found with them in the Gabb collection.^ 

 T. perattenuata of the Pliocene is clearly distinct from tornata by its 

 much slower taper, though all of the group are closely related. The 

 sculptural development of the series reached its acme in the upper 

 Oligocene when the most highly sculptured species, T. altilira, 

 became extinct. 

 Turritella calostemma n. sp. PI. 5, fig. 15. 



The shell resembles T. altilira Conrad. It is very long and tapers 

 slowly; the whorls are rather narrow, and the suture is not obvious. 

 The growth-lines are deeply arched across the visible part of the 

 whorls. On each whorl there is a high, narrow spiral ridge at the 

 upper fourth, its summit set with oblique tubercles. In the concave 

 interval following there are numerous spiral striae and a slightly 



2 Turritella perattenuata prcecellens n. subsp., PL 5, fig. 12. Even more slender 

 than perattenuata, the upper of the two prominent beaded cinguli being double, 

 the lower more acute, and in the later stages both are higher. There are several 

 small cords in the median concavity, three being more prominent than the others. 

 The growth-lines are inconspicuous, and retract strongly in the upper half of 

 the whorls. All of the specimens are broken. 



Length 57.5, basal diam. 8 mm.; 18 whorls. 

 ■ " 40 " " 1.3.7 " 5§ " 

 Cotypes No. 2608, A. N. S. P., collected by Wm. M. Gabb in Santo Domingo. 



