170 Exuviation in Shrimps and Lobsters. 



mixed upon the sides with golden yellow, and showing indications 

 of darker transverse bands upon the back ; upon the opercle a spot of 

 blue, continued towards the eye ; fins rosy pink mixed with yellow. 

 Upon the anterior part of the dorsal fin a deep black spot or blotch, 

 occupying the greater part of the membranes of the three first rays ; 

 another upon the upper margin of the base of the caudal fin. These 

 spots were similar in size and situation in Dr Johnston's spe- 

 cimens, and they continue unaltered in the spirits, although the other 

 colours have faded to a pinkish brown. 



As the specific title of Cornubicus has been applied to the other 

 species, and described as the Goldsinny by various writers subse- 

 quent to Pennant, it is proposed to designate the present species as 

 the Labrus (Crenilabrns) rupestris, (Jago's Goldsinny,) to which 

 the following synonyms may be appended. 



Goldsinny, Ray's Syn. Av. et Pise. App. Catalogus quorundum 

 rariorum, &c. D. Georgius Jago, p. 163, f. 3. 



Die Heekarausche, Lutjanus rupestris, Bloch. Naturg. der Aus- 

 landischen fische, ii. p. 117? ph 250, fig. 1. 



VII. — Observations on some circumstances attending the process of 

 Exuviation in Shrimps and Lobsters. By Jonathan Couch, 



F. L. S. 



Dr Milne-Edwards, in his Histoire Naturelle des Crustaces, 

 has given an account of what may be considered the present state of 

 our knowledge, of the circumstances under which the process of ex- 

 uviation is effected, and the methods by which it is accomplished 

 in the long-tailed stalk-eyed crustaceans ; but as much of what that 

 eminent naturalist advances is derived from other authorities, and 

 I have reason to conclude, contrary to the general opinion, that the 

 circumstances attending this process of nature, are different in even 

 nearly allied species, there still remains space for enquiry. 



Reaumur is our only original authority for the minute circum- 

 stances attending the process of exuviation, which he observed in the 

 River Crayfish (Potamobius fiuviatilis, Leach ;) but not having an 

 opportunity of consulting that author's work, I copy his narrative 

 from Dr iVl . Edwards's quotation : " A few days previous to the com- 

 mencement of the operation, the creature abstains from all solid 

 nourishment, and the carapace and abdominal segments will be found 

 to offer less than the usual resistance to the pressure of the finger. 

 Shortly afterwards the crayfish appears restless, and rubs its legs 

 against each other ; it then throws itself on its back, agitates its 

 whole body and then distends it, by which the membrane joining 



