24 FOSSIL MALACOSTRACOUS CRUSTACEA. 



me from giving any detailed generic character. I was led, however, from the general 

 form of the carapace, the great similarity of its granulations, the identity of the tubercles 

 on the surface, and of the teeth on the latero-anterior margin, and the form and direction 

 of the orbits, to believe that it must be nearly related to the recent genus Matuta. 



It differs, however, from that genus in the structure of the outer footjaws, which 

 in the recent form are acutely triangular, being broad at the base, and extending forwards 

 to an acute apex, of which figure the second joint forms a continuous part ; whilst in the 

 fossil genus, this, the only remaining portion of those organs, is linear, elongate, and 

 rounded ; in this character it also deviates from the group to which Matuta belongs. 

 Notwithstanding this discrepancy, however, the narrowing of the buccal opening forwards, 

 in an outline which as far as it is perfect in the specimen is sufficiently similar to that 

 in Matuta, indicates a close approach to the family type, and in the unfortunate absence 

 of all other parts, particularly of the limbs, which in this group are so characteristic, 

 I felt justified in giving it conditionally a station amongst the Oxystomata, and in the 

 matutiform section of the family Calappadse. 



Specimens of this species are in the British Museum, and in the collections of 

 Mr. Bowerbank and Mr. Wetherell, and are all from the Isle of Sheppey. 



Sub-Order— OXYSTOMATA. 



Family— CORYSTIDtE. 

 Genus — Cyclocorystes, Bell. 



Species unica. Cyclocorystes pulchellus, mild. Plate IV, figs. 1, 2. 



Descr. Carapace nearly circular, somewhat contracted posteriorly ; front advanced, 

 horizontal, broad, slightly waved and minutely emarginate, without any armature ; 

 latero-anterior margin with- a few very small, irregular, granulated teeth ; latero-posterior 

 margin rounded (posterior margin broken away in the only specimen known) ; regions 

 flattened, distinctly and evenly granulated, the separating furrows smooth, and a round 

 smooth patch between the hepatic and branchial regions, and another between the 

 epibranchial and metabranchial lobes ; frontal and orbital margins, and the pterygostomian 

 processes granulated ; gastric region separated by a broad, smooth furrow from the front. 

 Protogastric lobes separated from each other by a long, linear, granulated process of 

 the mesogastric ; cardiac region pentagonal. Orbits nearly round, open above, without 

 any fissure, the margins even and simple, the hiatus at the inner angle small, and probably 

 filled by the basal joint of the external antennas ; autennary fossae transverse, the roof even 



