120 



ADDITIONS TO "BRITISH CONCHOLOGY." 



(Continued from page 74). 



By J. T. MARSHALL. 



The Cithna tenella of Jeffreys was dredged in the Fserce Channel 

 by the ' Lightning ' and ' Triton,' and off the Butt of Lewis by 

 the ' Knight Errant.' Some abyssal specimens from the Atlantic 

 are found to be sculptured, similarly to Aclis waller i from the 

 same depths. These sculptured Cithntz Jeffreys named var. costulata, 

 and included with them C. margaritifera Wats., an abyssal Pacific 

 shell which he had previously advised Dr. Watson was new. Jeffreys 

 gives no reason for changing his mind as to the latter, but probably 

 when he compared Watson's shell with C. tenella he had not then 

 noticed the sculptured specimens from this particular depth, which 

 were very few ; in addition to which he was working against time at 

 the end, and overlooked many things, ultimately leaving the 'Light- 

 ning' and 'Porcupine' Reports unfinished. Dr. Watson, in the 

 absence of any explanation from Jeffreys, prefers to leave his species 

 as it stands, 1 though I do not see any grounds for their separation, the 

 Pacific and the Atlantic forms appearing fairly identical with the ex- 

 ception of a slight difference in the contour of the Pacific shell, which 

 is not strange considering the enormous space between the two 

 stations. In any case, Watson's name stands first for the sculptured 

 form. Another character which some of these deep-water Cithnce 

 and Aclis have in common is that the last whorl is peculiarly malle- 

 ated, as is sometimes seen in the freshwater genus Limncea, 



Littorina obtusata L. — In some sheltered coves the shells of 

 this species are covered with a conspicuous striated epidermis, 

 approaching that of Velutina. In the male the body-whorl is nar- 

 rower, the aperture smaller and less expanded, and the spire more 

 produced, but flattened at the apex. Adults of both sexes occur of 

 all sizes, from i '05 to 6 lines in length, although the males are much 

 less numerous. In rare cases the shell is bicoloured, having a yellow 

 spire and brown body-whorl, or vice-versa. 



Var. neritiformis Brown — Occasionally found with the type in 

 many places, but abundant at Weymouth and Portland. Brown's 

 figure is a useless one, but Forbes and Hanley's figures (pi. 84, f. 3, 4) 

 are very good. 



Var. ornata Jeffr. — Smaller and rounder ; spire more produced 

 and pointed ; colours equally variable as in the type ; not necessarily 

 banded. Guernsey, plentiful ; Weymouth, rare. The male typical 

 shell has a produced but flattened apex ; in this variety it is produced 

 and pointed. 



1 ' Challenger' Gasteropoda, p. 580-1, pi. xliii., f. 3. 



