33 



had not been disturbed when brought to me, There was 

 no byssus. The same species is sometimes found on the 

 shore. 



* M. DISCREPANS. Mytilus D. Mont. Test. Brit., 

 vol. 1, p. 169. Modiola D. Flem. Brit. An., p. 413. 

 Abundant on rocks, attached by a byssus to the stems of 

 the common Coralline. It is also frequently found embed- 

 ded in the substance of a species of ascidia: in a manner 

 not easily to be accounted for, but in which situation 

 it grows to a much larger size than when openly exposed, 

 and with much more beautiful colours. When thus en- 

 closed, the syphon pierces the tunic of the animal, and 

 thus preserves its commuication with the water. 



M. DISCORS. Mytilus D. Mont. Test. Brit., vol. 1, 

 p. 167. Modiola D. Flem. Brit. An., p. 413. Common, 

 but less abundant than the last species ; I have never found 

 it buried under the tunic of an Ascidia, like the last named 

 species. 



M. GIBBSli. Flem. Brit. An., p. 413. Of this rare spe- 

 cies I have seen only one specimen, presented by a Lady. 



M. BARBATUS. Mytilus Curtus. Turt. Lin. Pen. Brit. 

 Zo. vol. 4, pi. 64, fig. 76. M. B. Mont. Test. Brit., 

 vol. 1, p. 161. 



Dr. Fleming confidently pronounces this to be a variety 

 of Modiolus Vulgaris ; with which opinion neither Montagu's 

 nor mine can agree. It is not rare ; but whether the follow- 

 ing is a younger growth or separate species, must be left for 

 further research. It is provisionally named, for it differs 

 considerably from a foreign shell marked M. Barbatus in 

 the museum of the Royal Institution ; and I have found 

 the Cornish shells so named, so commonly fixed amongst 

 specimens of Mytilus Incurvatus, a shell which from its 

 exposed situation soon becomes naked and worn, that I have 

 doubted whether it be not the young of that species; an 

 opinion which seems to have been held by Pennant. 



* M. MINUTUS. It is minute ; and many specimens were 



found among a multitude of the Kellia rubra, studding 

 the fibres of a small green sea weed, on which they appear 

 to have been feeding. It is about as deep as long, and 

 along the side of the hinge thinly studded with short firm 

 hairs. It is not attached by a byssus, and seems capable 

 of motion, like the Kellia. 



MYTILUS. 

 GENERIC CHARACTER: Shell longitudinal, the valves 

 equal, regular, pointed at the base, fixed by a byssus. 

 Beaks almost strait, terminal, pointed. Hinge lateral, 

 usually without teeth. Ligament marginal, subinternal. 

 One elongated, clavate, sublateral muscular impression. 



