272 PALEONTOLOGY OF NEW YORK. 



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

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

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

 minute, obliquely conical pustules, in some cases seeming to become 

 spinulous."* 



Forms with this characteristic modification of the loop may be designated 

 by the term Romingerina.j 



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 Juvavella. Their brachidia 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 Qj]hlert, 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- 

 seljERIa, 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 Rhynchospira, Tre- 

 matospira and Zygospira. The brachidium has been isolated in none of these, 

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



* Pi-oc. Acad. Nat. Sci. Philadelphia, p. 405. 1S62. 



t Dr. Cakl Romingeb, to whom this genus is dedicated, was the tiist American investi{,''ator who suc- 

 ceeded in producing satisfactoi-y translucent preparations of the fo.ssil brachiopods with calcitied bi-aohidia. 

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

 Volume IV of the Paleontology of New York, as there recognized, were based upon his preparations. 



