﻿ACTINOPTERIA. 



63 



ornament and other points, and its right valve bears much the same relationship 

 to the right valve here described from Lummaton, that the respective left 

 valves do. We are therefore led to the belief that the English right and left 

 valves belong to one species ; and this belief is confirmed by comparing them 

 together. The ornament of the right valve appears to agree with that of the left 

 in essence though not in development, while it does not seem to me to do so with 

 the left valves of any of the accompanying species. 



The specimen from Lummaton is interesting from showing a curious mending 

 of an injury to the shell during life. 



Under the name Actinoptera manca, Barrois 1 describes a very kindred species, 

 which seems chiefly to differ in being rayed only over the central part of the 

 surface, and in having more lamellar transverse markings ; the latter point, 

 however, may perhaps be an accidental effect of age or sediment. Possibly it 

 may prove identical. BarrandeV original Avicula or Myalina manca seems to 

 differ in shape and in the coarseness of its ornament. 



Affinities. — Pterinea perdita, Barrande, 3 resembles the right valve in ornament, 

 but is a very much shorter shell, and has the transverse strige much less curved. 



Pterinea (Actinoptera) Trigeri, (Ehlert, 1 seems distinguished by having no rays 

 whatever on the right valve, and no regular fine strias on the left valve. Its 

 anterior wing cannot of course be compared with that of our shells. It evidently 

 is so closely allied as to be on the verge of identity. 



3. ACTINOPTERIA MUSICATA, 11. Sp. PI. VI, figS. 7, 7(1, 7b. 



Description. — Left valve large, flatfish, transverse, sub-quadrate, oblique. 

 Umbo rather small, situated at the anterior end of the hinge-line (excluding the 

 anterior wing, which is unknown), oblique, flattened, proximate. Hinge-line long, 

 straight, nearly equal to the greatest extension of the shell behind. Anterior 

 margin probably narrow and oblique. Inferior margin wide, moderately convex. 

 Posterior margin slightly oblique, sigmoid. Posterior wing large, sloping, 

 undefined. Contour of surface slightly convex, steeper in front, slightly concave 

 behind the post-umbonal line. Surface ornamented by a major series of thirty or 

 forty fine, low, narrow, rounded, and very distant rays, between each of which are 



1 1889, Barrois, 'Faun. Calc. d'Erbray,' p. 175, pi. xii, figs. 1, 1 «, 1 b. 



- 1881, Barrande, ' Syst. Sil. Bohcme,' vol. vi, pi. ccxxii, figs. 8, 0, Et. F. 



3 1881, ibid., vol. vi, pi. cxxv, figs. 1—3, Et. F. 



* 1S88, (Ehlert, ' Bull. Soe. Geo!. Fr.,' ser. 3, vol. xvi, p. 64G, pi. xiv, figs, 4, 4 a. 



