﻿REPORT OF THE DIRECTOR I9IO 165 



leave it in that genus until better material is available. This material 

 will be found upon careful search in the Carbonic limestone of Nova 

 Scotia. 



Externally, this species resembles Productus tenuicosta 

 from the type locality, though it is much smaller and much less pro- 

 duced anteriorly. The full elucidation of the internal characters of 

 both species may show them to be identical, but at present this seems 

 unlikely. 



Since this discussion was written a copy of Girty's paper, 1 in 

 which he describes the new subgenus Diaphragmus, has come to 

 notice. The character upon which this subgenus is based is exhibited 

 in specimens from the Chesser Group and in a fragmentary specimen 

 figured later from the Moorefield shales. The specimens from 

 older rocks at Cape le Trou and Oyster basin have this feature well 

 developed. Indeed there is some suspicion of its presence in what 

 may be Strophalosias from the latter locality. This character seems 

 to have originated as early as the lowest Kinderhook or later 

 Devonic in such shells as Productus dissimilis Hall, and 

 reached its fullest development in Marginifera muricata, 

 M. splendens, and M. w a b a s h e n s i s. The presence of the 

 " plate " or " diaphragm " is to be regarded as the inception of shell 

 deposition in the peripheral region of the brachial valve together 

 with its geniculation and later became more and more pronounced 

 resulting in sharp murication of the Pennsylvanic species. Since 

 somewhat similar characters occur in other shells of the Stropho- 

 menacea the structure is of doubtful systematic significance at best, 

 and the splitting up of the subgenus Marginifera on the basis of 

 the extent of the deposit seems hardly warranted. 



Productus doubleti nov. 

 Cast small, gibbous, strongly arcuate longitudinally, most arcuate 

 near the beak. Beak inflated, broad and full, extending but slightly 

 beyond the hinge. No marked sinus pres- 

 ent, central part of shell but slightly flat- ^ T|| 

 tened in transverse profile ; nearly equally 



arcuate when viewed from side or front. Producttts doubleti nov. 

 Hinge about equal in length to the greatest ^T^tfe^e! views ° f 

 anterior width of the shell. Lateral mar- Cape le Trou ' Grindstone L 

 gins slightly arcuate, rounding into the convex front of the shell. 

 On the surface there are 36 coarse radiating striae, those in the 

 central part of the shell being coarser than those on the sides. No 



'Ann. N. Y. Acad. Sci., XX, 3, II, p. 217, 1910. 



