122 PALAEONTOLOGY OF NEW YORK. 



form and acute apex that it could not have been tubular, and, besides, there is 

 no evidence of a perforation in the plate. 



The spirals have the same structure as in Eu- 

 METRiA, and Derbv has shown that the posterior 

 margins of the coils are fimbriated. The loop, also, 

 is quite similar to that of Eumetria Verneuiliana. 

 Waagen has represented it in Eumetria (Hustedia) 

 grandicosta, Davidson, as terminating in a short, Loopor iJusMJjiLmom.Marcou. lo 

 sharp, retrally directed stem, but in the American specimens this stem appears 

 to be much longer and the posterior edges of the lamellae both of the stem and 

 the lateral branches are furnished with divergent spinules. In all our prepara- 

 tions the extremity of the stem appears to be simple. 



The exterior of the shell is coarsely plicated and the structure strongly 

 punctate. 



The representation of this genus of shells in American faunas is restricted, 

 so far as known, to the species H. Mormoni*, which occurs in the upper Car- 

 boniferous of Missouri and Kansas, and has been identified by Derby in the 

 Coal Measures both of Brazil and Peru. The two species described by Waagen 

 from the Salt-Range of India as Eumetria grandicosta, Davidson, and E. indica, 

 Waagen, belong to Hustedia, and probably also Retzia (Terebratula) radialis, 

 Phillips, Retzia carbonaria, Davidson, and R. (Terebratula) ulothrix, de Koninck 

 from the British Coal Measures. Retzia ulothrix, R. radialis, R. Davidsoni, R. in- 

 termedia, de Koninck, occur in equivalent faunasin Belgium.f 



It is probably true that the various species from the St. Cassian beds, which 

 have been referred by BittnerJ to the genus Retzia, have their closest 

 relations with Hustedia. These are, for the most part, coarsely ribbed forms, 

 some of them with extravagantly high areas. Their internal structure has 

 not been satisfactorily demonstrated. 



* Whether the other American Carboniferous species, Retzia compressa. Meek; R. Woosteri, White; 

 R. Meekana, Shumard, and R. papWata, Shumard, are congeneric with H. Monnoni, is not yet deteimined. 



t See Davidson, Cartioniferous Brachiopoda, pp. 87, 88, 219, pi. xvii, figs. 19-21 ; pi. xviii, tigs. 14, 15; 

 pi. 1, figs. 3, 4-9 ; and de Koninck, Faune du Calcaire Carboniffere de la Belgique ; Brachiopodep, Explic, 

 pi. xxii, figs. 1-4, 10-19. 



t Brachiopoden der alpinen Trias, 1890. 



