Par ] es 
XXXI. Hors Carcinologicæ, or Notices of Crustacea. I, A Monograph of the Leuco- 
siade, with observations on the relations, structure, habits and distribution of the 
family; a revision of the generic characters; and descriptions of new genera and 
species. . By Tuomas Bunt, Esq., V.P.R.S., Pres. L.S. &c. ; 
Read June 5th, 1855. 
THERE is not perhaps another family amongst the whole of the Decapodous Crustacea 
so distinctly isolated by its general characters as the Leucostanæ. Belonging, as they 
obviously do, to the large tribe of Ozystomata, to which they are allied by the important 
character of the form of the buccal cavity and the structure of the foot-jaws, they have in 
many respects but little tangible affinity with any other family of that group, by means of ` 
intermediate aberrant forms, with the exception of a certain primé facie approach to the 
Calappade in the genus Oreophorus, to which further allusion will be made. 
And not only is there such a remarkable absence of any osculant form within the limits 
of this very natural group, but there is a no less striking want of any obvious approxima- 
tion to this type in the other families of the Oxystomata; for the relation suggested by 
De Haan of the genus Matuta, or rather his family of Matutoidea comprising Matuta 
and Hepatus, as leading to the Leucosiade, appears to me quite devoid of any sound 
foundation. Still less appearance is there of any important approximation to the Rani- 
nade, as suggested by the same learned writer. — Jti 
I cannot, however, but believe that there is a structural approach to this family in a 
genus which has hitherto been placed at a remote distance from it by all the authorities 
on this subject, and particularly by Professor Milne-Edwards in his recent admirable 
treatise, as it may be called, on the Catametopa. I allude to the genus Pinnotheres, which 
in the work above mentioned is associated with the families Grapside, Gecarcinide, Ocy- 
phat! &c., to which groups its affinity is probably much more slight than to the family 
now under consideration. It will be reserved for a future occasion to examine into the real 
relations of the somewhat anomalous family of the Pinmotheride ; but I would observe, 
that the general aspect of the male Pinnotheres is so similar to that of a true Leucosia 
as to be obvious at the first glance; and although I would not trust too much to external | 
form and general character or aspect, I think these po on Bi sin idic ipi 
rated. "There is frequently a physiognomical character, so to speak, which is Y o 
some close relation of affinity, which ought not to be cast aside hastily and wi hou > 
consideration as a mere analogical resemblance. I shall not on the present reprit x 
into a detailed investigation of the relation between these up mdp ef oth pi 
that the form of the buceal opening, the foot-jaws, He jc ey me m Poe ; 
portant or gans appear to me to afford pian — i joda e se 
The approach of the genus Oreophorus to the Calappade is, however, que , 
