BIVALVIA. 59 



as only a variety of M. modiolus. A greater curvature in the ventral margin, and the 

 expansion on the posterior side, are deviations from the ordinary form of the larger 

 and more common species, and these are, I presume, the principal characters relied 

 upon for separation. On the exterior are a series of ridges or elevated lines of 

 growth, the probable remains of the support of the bearded or fringed portion of the 

 epidermis when in a recent state. The beaks in this specimen appear to be terminal, 

 the anterior side of the shell not projecting beyond them, and in that character 

 more resembling Mytilus, which it closely approaches in form ; there is, nevertheless, 

 a projection outwards, like the rest of the genus. The ventral margin is somewhat 

 incurved, the dorsal portion of the shell a good deal flattened behind, and extending 

 beyond the ligamental area, while the centre is tumid or inflated ; the dimensions 

 of the widest part, which is on the posterior side behind the ligament, is twice that of 

 what it measures across the shell immediately behind the umbo. 



3. Modiola phaseolina, Philippi. Tab. VIII, fig. 4. 



Modiola phaseolina. Phil. En. Moll. Sic, vol. ii. p. 51, t. 15, fig. 14, 1844. 



— — Jeffreys. An. Nat. Hist., vol. xix, p. 313. 



— — Forb. and Hani. Hist. Brit. Moll., vol. ii, p. 186, pi. 44, fig. 3, 



1849. 



Spec. Char. Testa oblong o-ovatd, Icevigatd, tenui, margine ventrali recto ; subsinuato, 

 dorsali subangulato, cardine cremdato. 



Shell oblong-ovate, smooth and thin ; ventral margin straight or subsinuated, 

 dorsal margin subangulated ; cardinal area crenulated : shell nacreous. 



Locality. Coralline Crag, Sutton, and Ramsholt. 



Recent, Britain, and Mediterranean. 



The distinguishing character of this species appears to be the finely crenulated margin 

 of the dorsal edge on the outside of the ligamental area, as the outer form or contour of 

 the shell is variable like M. modiolus, from the young of which it could not be separated 

 by any character which might not also be applied to that species ; some specimens have 

 but a short hinge line, with a somewhat rounded dorsal edge, and a subcylindrical or 

 ovato-oblong outline, while in others there is a considerable angle on the dorsal edge 

 at the posterior termination of the ligament, and the ventral margin is nearly straight, 

 varying sometimes from that line a little, both outwardly and inwardly. The largest 

 specimens which have a minutely crenulated hinge line do not exceed f ths of an inch, 

 and all show a pearly texture. The umbo is generally terminal, although the anterior 

 side will occasionally be seen to project beyond it. 



This, as well as the preceding species, have been introduced in deference to the 

 Malacologists, but it is very doubtful if they will not hereafter have both to be united 

 with M. modiolus. 



