REPORT ON THE NUDIBRANCHIATA. 271 



One specimen of this species was found at Hilbre 

 (S. Archer). Byerley records it as having been also found 

 upon the western shore of the Mersey, near the entrance 

 of the river. Mersey and Dee, occasional (Collingwood). 



Tritonia pleheia, Johnston. 



Dredged north of Wirral (Byerley). Mersey and Dee, 

 occasional (Collingwood). 



This species was found on Hilbre Island at low-water 

 mark on May 17th, 1885 ; and was dredged in Hilbre Swash 

 on May 9th. 



Family. — Dendronotid^. 



Dendronotiis arhorescens, Miiller. 



This large and very beautiful species is usually one of the 

 commonest Nudibranchs at Hilbre Island. In mid-winter I 

 have found it in great abundance creeping over the stones 

 and seaweeds close to low-water mark. In some of the 

 L. M. B. C. expeditions to Hilbre, in early summer, on the 

 other hand, very few specimens were found ; but later on, in 

 July, Dendronotiis was again abundant. Mr. Price and Mr. 

 Byerley record it from Hilbre, New Brighton, and Woodside 

 Slip, but say that it is (1855) by no means so abundant as in 

 former years. I am inclined to think that these variations in 

 the abundance of this species at Hilbre are due to a habit of 

 migrating periodically from the shore into deep water. It is 

 intended in future expeditions of the L. M. B. C. to Hilbre 

 Island to make careful observations upon the relative 

 abundance of this and other species. 



Recorded from the Isle of Man by Forbes. 



This species was dredged during the cruise of the 

 " Hyaena " off the Great Ormes Head, from a depth of seven 

 to eight fathoms, and was obtained during August between 

 Port St. Mary and Spanish Head, Isle of Man, from a depth 

 of twenty fathoms. 



