EUCORYSTES. 17 



Obs. The distinctions between this and all the other species of the genus are well 

 marked. In the number of tubercles on the carapace it is intermediate between P. 

 Broderipii and P. Slokesii, having much fewer than the latter species. It is much more 

 convex, the margin is more rounded than in either of the others, and the latero- 

 posterior margin, instead of passing backwards to its junction with the posterior in 

 almost a straight line, as in P. Stokesii, is gradually and evenly curved. 



Genus — Eucorystes, Bell. 



Char. Gen. Testa trapezoidea, depressa, dimidio anteriore sculpto in elevationibus 

 contortis, linearibus, sulcis separatis ; dimidio posteriore lsevi, granulato ; fronte lato. 

 Orbita magna?, latae, margine elevato, usque ad angulos antico-laterales tendentes, supra 

 bifissse, infra unifissae. * 



Species unica. Eucorystes Carteri, sp., M'Coy. Plate II, figs. 14 — 17. 



Descr. Carapace depressed, somewhat trapeziform, nearly as broad as it is long, not 

 greatly narrowed either anteriorly or posteriorly ; the anterior half curiously sculptured, 

 the surface being divided by numerous, variously formed, nearly linear, flattened ridges, 

 which are separated by sulci of about equal width. These ridges are minutely granulated, 

 with a line of somewhat larger granules on their margin, some of which are insulated. 

 The elevations are not, as Professor M'Coy would intimate, absolutely identical with the 

 different regions or lobes of the regions, although they in some measure indicate them, 

 and the metagastric lobe, in particular, forms a dagger-shaped elevation, of which the 

 anterior process, extending forwards to the front, represents the blade ; the other 

 ridges are in pairs, excepting a broad median one on the urogastric lobe, extending 

 far to each side, and they are all symmetrical ; the posterior half of the carapace is 

 slightly granulated ; the latero-anterior margin has two obtuse processes besides the 

 external angle of the orbit ; the latero-posterior margin is nearly straight, and the posterior 

 very broad, with the angles rounded. The rostrum is tridentate, the lateral teeth being 

 longer than the central. The orbits are transverse, excessively large, each occupying 

 about a third of the anterior margin of the carapace, and extending to the external angle, 

 where there is a small, blunt tooth ; they are about half as broad as they are long, oval, 

 directed forwards, slightly contracted in the middle, and apparently open to the antennary 

 fossae ; their margins are raised, simple, and there are two fissures on the upper, and one 

 near the inner angle in the lower ; the front occupies the middle third of the anterior 

 margin of the carapace. 



3 



