MONOGRAPH OF THE LEUCOSIADÆ. 295 
Genus LEUCOoSILIA, Bell. 
Cuar. Gen.—Testa orbicularis, subglobosa, fronte dentibus binis divergentibus terminatä; regione in- 
testinali unidentatä. Fosse untennarie oblique, e dentibus frontis excavate. Orbita fissuris tribus. 
Pedipalpi externi caule exteriore subeurvo apice obtuso. Pedes antici robusti, longitudine mediocres. 
Abdomen Marıs segmentis tertio, quarto, quinto coalitis, penultimo unidentato,—Faw1N lat? 
ovatum, valdé convexum. 
Species unica, LEUCOSILIA JURINII (Tas. XXXII. fig. 1). | 
Guaia (Ilia) Jurinii, Sauss. 
Hab. ad insulas Galapagos. Muss. Brit., Bell. 
Carapace orbicular, very convex, the sides rounded, the surface covered with large con- 
tiguous granulations, excepting on the frontal and part of the hepatie regions, which are 
smooth: there is a small elevation on each hepatic region. The front with two small, 
triangular, divergent teeth, forming the hood-shaped roof of the antennary fossæ, which 
are oblique and open. Orbits with three small fissures. There is a single obtuse tooth 
or tubercle on the intestinal region. External pedipalps with the outer branch very 
slightly curved, not dilated as in Myra, nor narrowed forwards as in Persephona, but 
with nearly parallel margins. Abdomen in the male very long, triangular, the penulti- 
mate segment with a strong, sharp tooth directed. backwards; in the female broad oval, 
very convex, with a broad central carina. The whole body above and below, with the 
exception before stated, covered with large granulations. Anterior legs much resembling 
those in Persephona, half as long again as the carapace, the arm granulated, the hand 
short and thick, the fingers very slightly curved, armed with very small distinct tubercles, 
the points crossing a little when closed. 
Length of carapace 0°8 in. u 
The grounds upon which I have considered it necessary to constitute this species a 
separate genus from. those with which it is most nearly allied, particularly from Perse- 
phona, are perhaps rather to be found in its general habit and aspect, than in any very 
prominent distinctions in the structure of those organs upon which the generic characters 
are usually understood to depend; although even in these essential respects there are 
sufficient peculiarities to justify the separation. It is impossible not to be struck at first 
sight with the remarkable globular form of the body in each sex, so different from the 
oval form of Myra and of the male of Persephona, as well as from the depressed character 
of both sexes of the latter genus; whilst the existence of only a single small pang on 
the posterior part of the carapace removes it obviously from all the species of ; ^ ese 
genera, which have invariably three teeth at that part ; and from Ilia, in which there are 
four. The general form of the body approaches the last-named genus ag a roid 
other, but i its more important characters it is essentially different from it. From Per- 
en the antennary fossæ, and consequently in that of the front, 
sephona it differs in the form of ud 
3 cavities in the present genus. 
the two teeth of which form the roof of ra which has received from M. de Saussure the 
This species appears to be the same as tha i i L 
name ee; (Ilia) Jurinii,” and there are several specimens in the British Museum 
