MOLLUSOA OP PLYMOUTH. 447 



on the shore at Wenibury by Mr. Bourne on the 5th of May this 

 year, and on the 16th August Dr. Fowler dredged one large 

 specimen, 1^ inches long, of a dark, steel-grey colour, and five small 

 ones, ^ inch long, of which two were almost entirely white in colour, 

 and the rest were dark steel-grey. 



Mr. Vallentin finds this species abundant at Falmouth on the 

 Helford mud-flats, where young specimens are to be taken from the 

 under sides of F^icus. Friele and Hansen (1. c.) also notice this 

 habit. 



31. Lamellidoris, Alder and Hancoclc. 



43. *Lamellidoeis aspeka, A. and H. 



This species has not been obtained since the date of the previous 

 Eeport. It was not found by Cocks at Falmouth, and seems to be 

 essentially a northern species. 



44. *Lamellidoris bilamellata, Linnseus. 



This species is common at Plymouth, as on most rocky coasts of 

 the North Atlantic ; curiously enough, it is not recorded by Cocks 

 from Falmouth. 



45. *Lamellidoeis sparsa, A. and H. 



This species has not been taken during the past year. 



32. GoNioDOEis, Forbes. 



46. *G. NODOSA, Montagu. 



This beautiful little species is very abundant at Plymouth, and 

 I have made use of it for the purpose of testing some of Alder and 

 Hancock's statements about the habits of migration of Nudibranchs. 

 In his account of the Nudibranchiate Mollusca of St. Andrews 

 Prof. Mcintosh wrote concerning this species, '' There is little to 

 be met with at St. Andrews in support of the statement of the 

 able authors of the Monograph in regard to the disappearance of 

 the adult animal and the growth of the young ; for the varying 

 sizes occur throughout the entire year, fine full-grown specimens 

 (1^ inches) being found in December as well as in March, April, 

 and May." 



In order to examine into this matter, therefore, I began in the 

 early spring of last year (1889) to keep a record of all the specimens 

 of this species observed or captured. During February, and espe- 

 cially during March, April, and May, large individuals (1 inch long) 

 were extremely abundant on the rocks below the Laboratory and 



