34 MARSHALL? ALTERATIONS IN ‘BRITISH CONCHOLOGY.’ 
some writers regard both these forms as only varieties of 
R. parva, and Dr. Boog Watson has well expressed the 
prevailing confusion of this group of /zssoa in the ‘Challenger’ 
Report, p. 588 :—“ Dr. Jeffreys regards FR. szmzlis Scac., as 
a small variety of 7. costulata Alder, a view I entirely share, 
with the addition that I believe both these and a great 
many other species, both British and foreign, to be mere 
varieties of 2. parva Da Costa. Perhaps, when all zoolo- 
gical classification has been reduced to chaos, and each 
museum specimen has received a separate name, a real 
revision of species will be entered upon. In the meantime, 
such labour is thrown away, and Scacchi’s species has as 
much right to recognition as the others around it.” 
Hydrobia similis and H. ventrosa should be expunged 
from Mr. Somerville’s List. Under no circumstances can 
they be regarded as marine species. 
Aclis unica Mont. Dr. Jeffreys in the ‘Lightning’ Report 
adopted this species as the type of his genus Cvonzscus, 
which differs from Acs proper in several respects. It 
has well-defined characters, and differs in the apex, the 
shape of the aperture, and particularly in having longitu- 
dinal strie. He has associated with it two other species 
taken in the ‘Porcupine’ Expedition—C. gracilis and C. 
striatus, 
A. gulsone Clark. In ‘ British Conchology’ the author had 
remarked that “this and A. wnica are aberrant forms of 
Aclis. Each has peculiar characters which render their 
systematic allocation very difficult.” | Having, therefore, 
suggested a new genus for the reception of A. unica, he 
proposed JZenippe for A. gulsone; but in his Appendix he 
altered that again to Pherusa, as Menippe was already em- 
ployed in the Crustacea. Clark, when originally describing 
the species, called it Pherusa. 
Odostomia scillz var. compactilis Jeff. (See ‘J. of C.,’ 
yol. vii., No. 8). 
J.C., viii., Apr., 1895. 
