1917.] NATURAL SCIENCES OF PHILADELPHIA. 37 



larger beaded central thread. Below the middle there is a second 

 but narrower spiral ridge, slightly tubereulate, and near the lower 

 edge there is a stronger spiral ridge, with convex, spirally striate, 

 weakly tubereulate summit. The specimens are fragmentary, but 

 indicate a length of at least 75 mm.; diameter of the largest fragment, 

 18 mm. It tapers a little more rapidly than T. aUilira. 



Haiti, 20 miles west of Azua. Also from between Las Cahobas and 

 Thomonde; collected by Mr. Lloyd B. Smith, 1914. 



This species differs from T. altilira by having three major spiral 

 ridges, the loAver two nearer together. In altilira and tornata there 

 are but two, and the upper one is sometimes doubled more or less 

 distinctly. In T. calostemma the upper ridge is simple. 



T. calostemma and T. altilira seem to be two lateral branches of 

 the T. tornata stock, highly accelerated in sculpture, reaching their 

 acme and becoming extinct in the upper Oligocene, while descendants 

 of the less specialized tornata stock held on to the Pliocene. Its last 

 incarnation, T. perattenuata, shows little advance in sculpture 

 beyond the Oligocene tornata; but it is specialized — probably over- 

 specialized — by its extraordinary length and large number of whorls. 



Petaloconchus domingensis Sowb. 

 Dentalium solidissimum n. sp. PI. 5, fig. 8. 



Known by a fragment which tapers rather slowly and is almost 

 circular in section. The shell is very solid, at the lower breach the 

 walls at least 3 mm. thick. It is sculptured with high ribs slightly 

 narrower than their intervals, their crests and the intervals being 

 rather strongly crenulated by circular strise. The superficial layer 

 has scaled off in great part, so that the finer sculpture described may 

 perhaps be due to wear. There are 28 primary ribs, and near the 

 larger end a few small interstitial riblets appear. Total length of 

 the fragment, 28.2 mm.; greatest diameter 15.8 mm.; diameter 

 14 mm. at the smaller end. 



This is probably a Fissidentalium, and from the fragment seems 

 intermediate between candidum and megathyris in taper. 



Dentalium cartagenense n. sp. PI. 5, fig. 10. 



A species of the group of Dentalium disparile. Moderately curved, 

 having seven angles, the intervals concave at the smaller, flat at the 

 larger end. The two intervals bounding the keel on the concave 

 side are wider than the others, and the three forming the curve of 

 the convex side are decidedly narrower than the rest. Intervals 

 have a few. longitudinal threads at the smaller end, increasing with 



