20 FOSSIL MALACOSTRACOUS CRUSTACEA. 



gibbous on the siuface ; the external antennae are not sufficiently perfect in any 

 specimen to enable me to say more than tliat the basal joint probably tills the hiatus 

 of the orbit ; epistonie rhomboidal ; extcrud footjaws twice as long as broad, and deeply 

 grooved longitudinally ; the abdomen exists in only one specimen, a male ; it has 

 the usual hastate form, and the third, fourth, ;uk1 fifth joints are united ; it is broadest 

 at the junction of the third and fourth joints ; anterior legs twice and a half the 

 length of tlie carapace, smooth and polished ; the wrist pentagonal, the hand somewhat 

 cai-inated above, the fingers nearly as long as the hand, the innno\eable one with a single 

 projecting tooth or tubercle on the opposing edge, the moveable one without any 

 ai'matm-e ; remaining feet quite simple and smooth. 



Dimensions of largest specimen: length of carapace, 09 hieh; breadth, 11 inch. 



Ohs. I have found considerable difficulty in satisfying myself respecting the affinities 

 of this remarkable form. In most respects, however, and those especially which are to be 

 regarded as the most important indications of relationship, it approaches the typical 

 Cancerida. The structure of the antennal region, the form of the external footjaws, the 

 figure of the carapace, and the arrangement of the abdominal segments of the male, 

 are similar to those of that family ; but the distance of the orbits, extending as tliey 

 do on each side as far as the middle of the hepatic region, indicate a marked approximation 

 to the tribe of the " Catametopa" of Milne Edwards. Perhaps its nearest affinity 

 is to Eriphiu, and between this genus and the Thelphusada^. The mutilated state of 

 the antennary organs, however, forbids my stating this with certainty. 



Numerous specimens exist in the collections of Mr. Bowerbank, of Wx. Wetherell, 

 of Mr. Prestwich, and in my own ; and there is a beautiful series in the British 

 Museum. They are all, as far as I have ascertained, from Sheppey and Southend. 

 Numbers of them are very small, and highly pyritic, some even having throughout a 

 metallic lustre. 



Family— VQ)KlV>mQM. 



Genus — Portunites, Bell. 



Char. Gen. Testa dimidio latior quam longior, depressa, marginc latero-antcriorc 

 quinque-dentato, dente posteriore reliquis longiorc. Orbitce supra bifissai. Pedipalpi 

 externi longitudinaliter sulcati. Pedes antici breves, robusti, inermes, digitis tuberculatis ; 

 reliqui graciles, laves (^«r quintum, anno ad natandum formatum?). Abdomen maris 

 hastatum, articulis a tertio ad quintum unitis; roijiiNiE ovatum, ai'ticulis omnibus 

 separatis. 



