1982 Mollusks. 



There can be little question that this fish belongs to the genus My- 

 liobatis of Cuvier, which is characterized by having the pectoral 

 expansion separated from the head, which organ becomes thus ex- 

 serted, after the manner of the genus Squatina, but from which latter, 

 among other important particulars, the present differs in having 

 the mouth placed far beneath the snout. In the adult state also, it is 

 marked by a small dorsal fin, and close behind it, is a lengthened spine 

 situated anteriorly on the caudal elongation. That in an embryotic 

 specimen the dorsal fin should be obscure, is not to be wondered at ; 

 for in numerous specimens of several species of the common rays 

 that I have obtained from the egg-case, I have constantly found the 

 caudal elongation to differ much from what is seen in the adidt fish ; 

 and I believe that all of them are at that period destitute of the ordi- 

 nary spines. It is probable that the direction of the expansion in the 

 pectorals, in this species, is subject to variety in different stages 

 of growth ; or these parts may have been compressed by the walls of 

 the case ; for in Mr. Yarrell's figure of what may be supposed the same 

 species ('History of British Fishes,' vol. ii. second edition), and in one 

 of Gesner's figures, in his c Nomenclator Aquatilium, (p. 121)' which 

 is copied from Belon, the pectorals are represented as extended at 

 right angles from the body ; while in another, in the same volume, the 

 extremity is directly obliquely backward ; as it is also in the sketch 

 taken from the present specimen. It may be from this direction of 

 the wings that this fish has been fancifully compared to a bird ; 

 and hence it is denominated a sea-eagle. Ruysch, whose figures are 

 for the most part copies from preceding authors without being im- 

 provements on the originals, has at Plate 9, fig. 9 given a tolerably 

 characteristic likeness ; and he remarks, that this fish has been called 

 sea-toad, from the resemblance of the form of the head to that crea- 

 ture ; and the comparison seems appropriate, from the elevation of its 

 head, and the lateral and projecting eyes. The same author, from his 

 own authority, says that this fish is viviparous ; an assertion which the 

 foregoing account shows to be incorrect. 



Jonathan Couch. 



Polperro. 



Habits of the Pond Mussel. — Having lately had a pond drained to within a few 

 inches of the bottom, I have had frequent opportunities of observing the economy of 

 the Anodon or pond mussel, of which there are great numbers in the mud. Their 

 manner of locomotion, though slow, is extremely regular, their tracks being very dis- 

 cernible in the soft mud. If the Anodon is furnished, as its congeners are, with a bys- 



