284 



REPORT ON THE STATE CABINET. 



Neither of these species are loiown to have the apex of the ventral 

 valve truncated. In another species, with extremely gibbous and arcuate 

 ventral valve and deeply concave dorsal valve, the disposition of the 

 reniform impressions is precisely like those illustrated ; and in none of 

 the species under investigation have we seen the least evidence of reni- 

 form impressions like those of figures 3 and 4, which are illustrations of 

 Permian species of Strophalosia. 



It is clear, therefore, that this character could not be relied on for 

 distinguishing the genus, if we were to include in it our Devonian species ; 



for in the three species referred to, the imprint 

 has the same direction and termination as shown 

 in AusTOLEGES, except perhaps that the muscular 

 scars may be a little nearer the hinge-line ; and 

 in this respect it is not very dissimilar to some 

 species of Productcts, as shown in P. costatus 

 (fig. 5), interior of the dorsal valve showing 

 the reniform vascular impressions, cardinal processes and the oblique 

 callosity C* 



I have, moreover, ascertained that the American forms of P. costatus 

 have often a well defined area on the ventral valve, and a narrow area 

 on the dorsal valve, extending nearly the entire length of the hinge-line ; 

 and in some specimens, this is as distinct as the area of Strophodonta 

 or of Chonetes. There is of course a foramen, which is open in the 

 examples observed ; though in Mr. Davidson's 

 figure of P. semireticulatus , cited above, the 

 foramen is closed by a deltidium. The speci- 

 mens of ventral valves of Productus, which 

 I have been able to examine, have no true 

 teeth or extensions from the margins of the 

 foramen ; but sometimes a callosity extends 

 obliquely backward and unites with the interior 

 of the shell, being in fact as much a representation of dental lamince as 

 we have in some species of STROPHODONTA.t The accompanying figure 

 6 is a dorsal view of Productus costatus, showing the hinge area. 



Thus we see that the species referred to Productus may have all the 



Fig. 6. 



* Productus longispinus and P. piistulosus have a similar form of the reniform impressions. 

 See Davidson's Monograph of British Carboniferous Brachiopoda. 

 t See Strophodonta demissa, S. reversa, S. nacrea and others. 



