MONOGRAPH OF THE LEUCOSIAD^. 295 



Genus Leucosilia, Bell. 



Char. Gen. — Testa orbicularis, subglobosa, fronte dentibus binis divergentibus terminata ; regione in- 

 testinali unidentata. Fossa antennaria obliquae, e dentibus frontis excavatas. Orbita fissuris tribus. 

 Pedipalpi externi caule exteriore subcurvo apice obtuso. Pedes antici robusti, longitudine mediocres. 

 Abdomen Maris segmentis tertio, quarto, quinto coalitis, penultimo unidentato, — Fosmin^: late 

 ovatum, valde convexum. 



Species unica, Leucosilia Jurinii (Tab. 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 hepatic 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 fossae, 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. 



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 tubercle on 

 the posterior part of the carapace removes it obviously from all the species of both these 

 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 more than any 

 other, but in its more important characters it is essentially different from it. From Per- 

 sephona it differs in the form of the antennary fossae, and consequently in that of the front, 

 the two teeth of which form the roof of those cavities in the present genus. 



This species appears to be the same as that which has received from M. de Saussure the 

 name of " Guaia {Ilia) Jurinii," and there are several specimens in the British Museum 



