274 



PALEONTOLOGY OF NEW YORK. 



Derby's Centronella ? Margarida, from the lower or middle Devonian of Matto 

 Grosso, Brazil, is a shell somewhat different from the foregoing species in 

 external expression, its size being smaller and its habit more retziiform. Its 

 author has compared it to the Retzia Wardiana, Hartt and Rathbun, of the 

 Erer6 fauna on the A.mazonas, a species which is suggestive of the Rhynchospira 

 lepida, Hall, of the Hamilton fauna of New York. Dr. Dekby has given a very 

 complete representation of the brachidium of the species, which arises from a 

 divided hinge-plate, bears the long, anterior plate characteristic of Renssel^ria, 

 and lacks any evidence of the posterior median extension or of a vertical 

 median plate. In the species which has been described as Rhynchospira lepida, 

 of the Hamilton shales of New York, and in the Centronella virgo (Terebratula 

 virgo, Phillips), from the middle Devonian of Torquay,* both very closely allied 

 in the character of the plicated exterior, there exists the same form of 

 brachidium. 



This combination of external and internal characters is thus a variant from 

 that of Centronella or Trigeria, but until our knowledge of these small shells 

 is further advanced, the species may be provisionally associated with Trigeria. ■ 



Fig. ISO. 



Fig. 191. 

 Notothyris subvescicularis, Davidson. 



FIG. 192. 



Fig. 190. A dorsal view of the exterior. 

 Fig. 191. A proQIe of the saraesliell. 



Fig. 192. Tlie interior of tlie brachial valve; showing the perforated hinge-plate and the lateral lamellse of the loop. 



(Waagen.) 



Reference has already been made to the fact that Waagen introduced the 

 name NoTOTHYRisf for a group of small, coarsely plicated, biconvex species 



* See preparations of the brachidium of this plicated species made by the Rev. Noeman Glass, and 

 given by Davidson, Devonian Brachiopoda, Suppl , p. 14, pi. i, tigs. 7-9. 1882. 

 t Productus-limestone Fossils ; Brachiopoda, p. 375. 1882. 



