BRITISPI DEVONIAN BRACHIOPODA. 17 



the upper edge of which, wlien viewed from the side, is flatly roof-shaped, while the 

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

 The surface of the loop and median plate is covered with minute obliquely conical 

 pustules, in some places seeming to become spinulous." 



The preparations of C. virgo made by Mr. Glass agree with the above description of 

 C. Julia, except in the following particulars : — First, Mr. Glass's preparations show the 

 crura as described by Billings and Rominger, but which Winchell's figures and descrip- 

 tions do not show ; and secondly, Mr. Glass found only a single ridge or plate, and not 

 a double vertical plate as described by Prof. Winchell. The details also of the extension 

 of this plate upwards and towards the ventral valve Mr. Glass was not able to ascertain, 

 nor was he able to find the " obliquely conical pustules " referred to by Prof. Winchell 

 as occurring on the surface of the loop and median plate. 



In the ' Sixteenth Annual Report of the Regents of the University of the State of New 

 York,' 1863, Professor Hall describes Centronella and Cryptonella at great length. His 

 description of Cryptonella is based upon the description of Centronella J alia by Winchell ; 

 but in the footnote containing the figures of Dr. Rominger's C. glans-fagea. Prof. Hall 

 withdraws the name of Cryptonella in favour of the older name Centronella^ on the ground 

 that Dr. Bominger's preparation of Billings' type shows that his description is erroneous, 

 and that the loop of C. glans-fagea and C. Julia are identical. In conclusion, it should 

 be observed that, according to Mr. Glass's preparations, the general outline of the loop of 

 Centronella is better given in the figures of Winchell and Hall than in that of Dr. 

 Rominger, and that Billings' figures are evidently founded on a mistake owing to im- 

 perfect preparations. 



Centronella virgo is a common species in the Middle-Devonian of Lummaton, near 

 Torquay, in Devonshire. 



Since writing the above observations, and in reply to a letter I had previously sent, 

 I have been favoured with a very kind communication 

 from Prof. Winchell. He could not send the preparations 

 of Centronella Julia from which his figures were origin- 

 ally drawn, but he sent to me a number of specimens 

 of C. Julia unworked, with the hope expressed that they 

 might afibrd the information desired. These specimens 

 were very small, and the matrix was of an arenaceous 

 and friable nature. Having sent the specimens to Mr, ^ , . , _ , „ , ,. 



" I Fig. 1.— Dorsal view of Centronella Julia, 



Glass, he was able by simply fracturing them in different showing the loop. 



'iG. 2. — Profile view, showing one band of 

 the loop with the vertical plate. 



directions to prove the truth of nearly every particular in 



Prof. Winchell's description. It was in this manner also From drawings (enlarged four times) by Prof. 



that Prof. Winchell had obtained his results, as he stated '^"'=''"' "'"^''''''^ '' ""'"■ 



in his letter to me. Ordinarily by this process no certain result can be obtained, and none 

 could be obtained in this manner from our Devonian specimens of the same genus. But 



3 



