1911.] NATURAL SCIENCES OF PHILADELPHIA. 359 



most perfect, has a very fine spiral striation. The last whorl has a 

 third rib, sub-peripheral in position, the base below it somewhat 

 convex, marked with some radial stria? and lamella?. 



On the early .whorls the spiral ribs are less prominent and the 

 interstitial beaded cords rather better developed. The embryonic 

 and early neanic whorls are unknown. 



T. tomato Guppy, known: to us by a series collected by Gabb in 

 Santo Domingo, is very closely related to T. altilira, but it differs 

 constantly, in a considerable series seen, by the far less prominent 

 spiral ribs. Whether this difference is to be regarded as specific or 

 as subspecific is not a matter of great importance. The Pliocene 

 T. terebrijormis Dall may be a descendant of the tornata stock. 



Gabb figured an allied form from the Miocene (?) of Sapote, Costa 

 Rica, as " Turritella altilirata Conrad." This name is either a mistake 

 or an emendation of Conrad's altilira; but the specimens are clearly 

 not that species. We propose to call Gabb's form Turritella sapo- 

 tensis, n. sp. (PL 27, fig. 10). Each whorl has a strong, compressed 

 spiral rib at the lower third, obliquely crenulated at its summit, as 

 in T. altilira. Above this rib the surface is a little convex, and bears 

 about five unequal spiral cords, crenulated and very low. The upper 

 two of these cords correspond in position with the upper spiral rib in 

 T. altilira. There is also a low cord above the suture. The broken 

 shell figured (which also served for Gabb's Pi. 44, fig. 9a) measures 

 29 mm. long, 15 mm. in greatest diameter, and consists of somewhat 

 over 3 whorls. 



Gabb's figure 9 misrepresents another fragmentary shell, which, from 

 the hard matrix which partly envelopes it, was evidently found with 

 T. sapotensis. So far as visible, it very closely resembles T. tornata 

 from Santo Domingo. It is clearly not T. altilira, nor do we think it a 

 younger stage of T. sapotensis, though such may possibly prove to be 

 the case. 



The age of the Sapote bed which furnished Gabb's fossils is uncer- 

 tain, dementia dariena (Conr.) is the only species known to be 

 common to this and the Gatun bed. Turritella is an excellent index 

 of small divisions in the Tertiary; T. sapotensis is apparently a deriva- 

 tive from T. altilira; and so far as that theory is of any value, may 

 indicate that the Sapote bed is later than the Gatun, perhaps Miocene. 



VERMETIDiE. 

 Petaloconchus domingensis Sowb. 



P. domingensis Sowb., Journ. Geol. Soc. Lond., VI, p. 51, PI. 10, fig. 9. 



An internal cast apparently of this species. 



