132 Mr. J. Wood-Mason on the Genus Deidamia. 
lately discovered by the ‘Challenger,’ and upon which Dr. 
v. Willemoes-Suhm (one of the naturalists to the expedition) 
had bestowed the name Detdamia, had long before been de- 
scribed by Professor Camil Heller under the name of Polycheles 
typhlops. In this remarkable Crustacean the organs of vision 
are morphologically entirely wanting, just as in Decdama, 
the position of the eye-stalks being merely indicated by two 
small black specks. The name Decdamia having been held 
to be inadmissible *, as having been already employed for a 
valid genus in another division of Arthropoda, and Willemoesia 
substituted for it upon the daring and, as it seems to me, 
dangerous assumption that every animal dredged up from so 
vast a depth as were the Deidamie would prove generically 
different from every thing previously described, I have thought 
it worth while to translate, for publication in the ‘ Annals and 
Magazine of Natural History,’ Professor Heller’s later and 
more methodical account of his wonderful blind Crustacean 
from the Mediterranean. The conclusions that I have arrived 
at, after a most careful study of Heller’s figures and descriptions 
in comparison with those published in Prof. Wyville Thomson’s 
Reports, are :— 
1. That the three species Polycheles typhlops, Deidamia 
leptodactyla, and D. crucifer cannot be placed in any existing 
family of crustaceans, recent or fossil, except perhaps the 
Eryonide, the structural characters of which are too incom- 
pletely known at present to admit of their being included 
In it. 
2. That the three species in question belong naturally to 
one and the same family. 
3. That they cannot be distinguished from one another even 
generically. 
I therefore beg to propose for them a new family name, and 
to regard all three as members of its single genus Polycheles, 
as follows :— 
Fam. nov. Polychelide. 
Genus unic. PoLYCHELES, Heller. 
a. With the four anterior pairs of walking-legs didactyle. 
Species 1. Polycheles typhlops, Heller. - 
2 crucifer, v. W.-S. 
b. With all the walking-legs didactyle. 
3. Polycheles leptodactyla, vy. W.-S. 
* ‘Nature,’ 1873, vol. viii. p. 485; 1874, vol. ix. p. 182. 
