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 
Erere fauna on the A.mazonas, a species which is suggestive of the Rhynchospira 
lepida, Hall, of the Hamilton fauna of New York. Dr. Derby 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 RENSSELiERiA, 
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, 190. Fig. 191. Fig. 192. 
Notothyris subvescicularis, Davidson. 
Fig. 190. A dorsal view of the exterior. 
Fig. 191. A profile of the same shell. 
Fig. 192. The interior of the brachial valve; showing the perforated liinge-plate and the lateral lamellse of the loop. 
(Waagen.) 
Reference has already been made to the fact that Waagen introduced the 
name Notothyris f for a group of small, coarsely plicated, biconvex species 
See preparations of the bi’achidiurn of this plicated species made by the Rev. Nokman Glass, and 
given by Davidson, Devonian Brachiopoda, Supiil , p. 14, pi. i, tigs. 7-9. 1882. 
t Productus-limestone Fossils; Brachiopoda, p. 37.0. 1882. 
