CONTRIBUTIONS TO PALEONTOLOGY. 



283 



Fig. 1. 



In reference to the Oenus Proddctus, Mr. Davidson remarks as follows : 



"All authenticated species of Productus hitherto examined have shown 

 themselves to be edentulous ; but whetlier this character was general and with- 

 out exception, may remain a question for further consideration ; anyhow, the 

 dorsal valve must have turned on its hinge-line with as much precision as 

 Chonetes, which possessed regularly articulating teeth. It has been often 

 asserted and believed that Peoductus might be distinguished from its sub- 

 genera by the total absence of an area; and although this is the prevalent 

 character of the genus, still in certain species, such as P. sinuatus, a perfectly 

 developed area is generally present in the ventral valve. There exists also an 

 occasional tendency to the formation of hinge-area in several species, as may be 

 seen, for example, in the remarkable example of P. semireticulattis, of which 

 a representation is given in Plate xliii, fig. 5." * 



These observations of Mr. Davidson are of later date than his " Intro- 

 duction to the Natural History of Brachiopoday 



One of the important features of distinction between Productus and 



Strophalosia has been stated to be fig- 2. 



the different disposition of the reni- 



form vascular impressions in the 



dorsal valve. The accompanying 



figures represent this character in 



two species of the latter genus — 



fig. 1, Strophalosia goldfussii ; fig. 2, 



Strophalosia morrisiana — as given by Mr. Davidson in his Introduction. 



In examining the species occurring in the higher formations of the 



New York rocks, which I had supposed might be referred to the Genus 



Strophalosia, I find evidence of a narrow area with small teeth and 



sockets in the greater num- 

 ber of species ; although 

 these features do not usu- 

 ally appear, except upon 

 the most critical examina- 

 tion. The disposition of the 

 reniform vascular impres- 

 sion, however, does not cor- 

 respond with that of Strophalosia ; but in all the species where this 

 feature has been observed it is similar to that shown in figs. 3, of Pro- 

 ductella onusta, and 4, of Productella striatula, enlarged to two diameters. f 



* Monograph of British Carboniferous Brackiopoda, p. 136, 1861. 



j B C, tooth-socket and socket-plate ; J, cardinal process ; O, anterior and posterior occlusors ; 

 V, the reniform vascular impressions ; F*, the faint diverging impression proceeding from the 

 extremity of the mesial septum. 



Fig. 3. 



