268 PALEONTOLOGY OF NEW YORK. 



genera Derbya and Orthothetes is very close, there are appreciable differences: 

 (1) in the general form of the shell; (2) the absence of true dental lamellae; 

 (3) the absence of a median septum in the pedicle-valve ; (4) the character of 

 tlie divaricating cardinal process. The structure of the last-mentioned feature 

 differs from that in Orthothetes and Derbya, in being thinner, sharper, much 

 higher and more deeply furcate The grooving of the posterior faces of the 

 tips of the cardinal process, as illustrated by Davidson,* gives to this organ a 

 very similar character to that in Triplecia Ortoni. 



As thus restricted, the genus has a comparatively meagre representation. 

 Seven species have been described from the Permo-Carboniferous of the Salt- 

 Range of India. Dr. Davidson had previously described one species, S. pectini- 

 formis, from the same country; and Dr. Derby described S. Hallianus, from 

 Itaiti'iba, Brazil. The only species known in European faunas is S. pelargoriatus, 

 and in North America the genus, so far as our present knowledge reaches, is 

 represented by a single species, S. Ulrichi, sp. nov. from the Chester limestone. 

 Dr. Waagen has divided the genus into two sections: I. Simplices, in which the 

 surface is simply covered with radiating striae; II. Plicati, in which the surface 

 is plicated as well as striated, as in Meekella. Of the former, S. pelargonatus, 

 Schlotheini, is a typical representative, and »V. Hallianus, Derby, of the latter. 

 In regard to the range of Streptorhynchus, this author observes : 



" The genus seems in Europe to be restricted to the Permian period, though 

 perhaps .some forms that occur in the Mountain limestone might also belong to 

 it. In the Salt-Range the different species are distributed through the whole 

 mass of the Productus limestone, from the lowest to the topmost beds. The 

 first section, the Sitnpliccs, is restricted to the lower and middle divisions whilst 

 the second section, the Plicati, chiefly occurs in the upper divisions." 



* Permian lir.ic.hiopoila, pi. ii, tig-. 39. 



