272 PALEONTOLOGY OF NEW YORK. 



" The upper edge where viewed fromthe side, is flatly roof-shaped, while 

 the lower edge describes two convexities, the greater anterior, leaving a notch 

 between them. The surHices of the loop and median plate are covered with 

 minute, obliquely conical pustules, ii\ some cases seeming to become 

 spinulous."* 



Forms with this characteristic modification of the loop may be designated 

 by the term RoMiNGERiNA.f 



After the disappearance of the Palaeozoic faunas, we again find in the Alpine 

 Trias (Hallstiitter-kalk) smooth, biconvex centronellids, less complicated in the 

 structure of the brachidium than Romingerina, even having the brachial sup- 

 ports smaller and more delicate, if not more simple in plan, than in Selenella. 

 These shells have been described by Bittner {loc. cit., p. 206. 1890) under the 

 generic term Jdvavella. Their bnichidia are very short, the lateral branches 

 but slightly expanded anteriorly and abruptly turned into a vertical plane. 



We may now turn to the consideration of the plicated centronellids which 

 have already been closely investigated by (Ehlert, and have received attention 

 from Waagen, Derby and Davidson. This discussion would with propriety 

 form a continuation of the observations already made upon the genus Rens- 

 SELiERiA, for it is the plicated and lineate shells of that genus which represent 

 the earliest appearance of the CENTRONELLA-type. The lower Devonian species, 

 from the west of France, in which Dr. CEhlert has determined the existence 

 of a centronellid brachidium, are all biconvex or subplano-convex species; 

 Terebratula Guerangeri, de Verneuil, is covered with strong rounded plications, 

 Centronella Gaudryi, CEhlert, with numerous fine plications, while on C. Bergeroni, 

 CEhlert, there are a few coarse angular ribs. All have a decided external 

 resemblance to certain spire-bearing forms of the genera Rhyncmospira, Tre- 

 MAT08PIRA and ZvGOSPiRA. The brachidium has been isolated in none of these, 

 but sections demonstrate that this structure in all these forms is similar to that 



* Proc. Acad. Nat. Sci. Philadelphia, p. 405. 1662. 



t Dr. Carl Rominobr, to whom this genus is dedicated, was the fii-st American investig-ator who suc- 

 ceeded in pi-oducing satisfactory translucent pi-epai-alions of the fossil brachiojwds with calcified brachidia. 

 Many of the determinations published in the Reports on the New York State Caliinet from 1861-67, and in 

 Volume IV of the Paljeontology of New York, as there recognized, wei-e based upon his preparations. 



