some British Fossil Crustacea. 163 



obtuse oblong nodules (defined by a hollow along each side 

 smoother than the rest of the carapace) ; branchial regions with 

 four large tubercles, two before and two behind, the inner 

 posterior one elongate obliquely backwards and outwards; 

 front four-lobed (including the prominent inner angle of the 

 orbit) j orbits large, the two lateral and the inferior angles pro- 

 minent ; latero-anterior margin with about three tubercles or 

 spines on each side, the posterior pair largest, placed at the 

 greatest width of the carapace, and in a line with the sulcus 

 separating the genital and cardiac regions ; surface minutely 

 and closely pitted; antennce as in Zantho (outer pair in the 

 inner canthi of the orbits, inner pair in deep transverse fossae 

 beneath the front) ; eyes on very short peduncles ; tail of seven 

 distinct pieces in both sexes ; first pair of feet forming robust, 

 unequal chelae ; hand subcompressed, nodulated, with the upper 

 and inner edge tuberculato-dentate ; fingers short, with few 

 large obtuse teeth ',four hind pair moderate, subequal, slightly 

 compressed, smooth. 



The Cancer Leachii (Desm.) may be looked on as the type of 

 this genus ; it was referred to Cancer or Zantho by Desmarest 

 (Consid. sur les Crust, fos.) and to Cancer by Milne-Edwards 

 (Suites a Buffon), from the want probably of good specimens. It 

 is nearer to Zantho by its tuberculated carapace, few tubercles on 

 the latero-anterior margins, and position of the external antennae 

 at the inner canthi of the eyes, instead of between these and the 

 front ; but it differs in the great convexity of the carapace, and 

 materially from both those genera in both sexes having seven 

 separate joints in the tail, showing in this a closer relationship 

 with Pilumnus, from which however the strong nodulation of the 

 hind part of the carapace and its oval, vaulted form, as well as 

 the quadrilobed front and great extent of the gastric region, di- 

 stinguish it. 1 only know the genus from the London clay. 



Zanthopsis nodosa (M'Coy). 

 Sp. Char. Carapace about one-seventh wider than long, very gib- 

 bous in the middle, sloping gradually to the sides, more rapidly 

 towards the posterior margin, falling most rapidly and with an 

 abrupt curve towards the front ; anterior half broadly rounded, 

 each antero-lateral margin with three large, obtusely rounded, 

 nodular tubercles gradually diminishing towards the front; 

 tubercles of the branchial regions very prominent as large ob- 

 tuse nodules ; gastric region tumid with a shallow depression 

 along the middle ; genital region small, prominent, strongly 

 divided by a wide transverse depression, posterior half most 

 prominent, obscurely bilobed ; hollow space on each side of the 

 mesial regional ridge remarkably smooth ; chela of the male 

 rather larger than of the female, the upper ridge of the right 



11* 



