MONOGRAPH 



OF THE 



FOSSIL MALACOSTRACOUS CRUSTACEA 



OF 



GREAT BRITAIN, 



PART I. — Of those found in the London Clay. 



Order— BRA CHYUBA. 

 Sub-Order— OXYRHYNCHI. 



Family— UklKDM. 

 Genus — Mithracia, Bell. 



Char. Gen. Testa subglobosa, tumida, rostro integro, supra sulcato. Orbitce ovatse 

 supra bifissae. Antenna ad basin rostri insertae. Bedipalpi externi caule interiore sulco 



kmgitudinali diviso, caule exteriore lineari. Abdomen maris ? fcemin^e ovatum, 



segmentis omnibus separatis. 



Species unica. Mithracia libinioides, mild. Plate V, figs. 10 — 12. 



Descr. Carapace tumid, nearly globular, as broad across the branchial region as it is 

 long, exclusive of the rostrum, covered uniformly with small tubercles ; regions elevated, 

 distinct, the separating furrows narrow and smooth ; rostrum moderately projecting, entire, 

 with a small sulcus or depression above ; gastric region with distinct lobes ; the two proto- 

 gastric meeting at the median line and confluent ; the mesogastric triangular, and separated 

 by a distinct furrow from the two metagastric, which are rather distinctly marked ; the 

 urogastric twice as broad as it is long ; cardiac region gibbous in the centre ; hepatic region 

 rounded, raised and projecting at the margin ; the branchial very large, rounded, and tumid ; 

 orbits oval, slightly divided at the bottom into two portions by a small, transverse line ; 

 antennae inserted beneath the base of the rostrum ; external footjaws with the inner stalk 



2 



