246 



TWENTIETH REPORT ON THE STATE CABINET. 



*' mation of hinge-area in several species; as may be seen, for example, in the 

 "remarkable example of P. seinireticulatus, 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 Brachiopoda." 



One of the important features of distinction between Productus and 

 Strophalosia has been stated to be 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, as given by 

 Mr. Davidson in his Introduction. 



Fig. 3. Fig. 4. 



Strophalosia goldfussii. Strophalosia morrisiana. 



In examining the species occurring in the higher formations of the New- 

 York rocks, which I had supposed might be referred to the Grenus Stropha- 

 losia, I find evidence of a narrow area with small teeth and sockets in the 

 greater number of the species ; although these features do not usually 

 appear, except upon the most critical examination. The disposition of the 

 reniform vascular impression, however, does not correspond with that of 

 Strophalosia; but in all the species where this feature has been observed, 

 it is similar to that shown in figures 5 and 6. 



Eig. 5. Fig. 6. 



Prodtjctella onusta. Productella striatula. 



B. C. Tooth-socket and socket plate. (Enlarged to two diameters.) 



/. Cardinal process. 0. Anterior and posterior occlusors. V. The reniform 



vascular impressions. 



V* This letter refers to the faint diverging impression proceeding from the 



extremity of the mesial septum of P. onusta. A similar marking has been observed 



in another species, but no connexion with the reniform vascular impressions has 



been observed. 



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



