Yol. 54.] THE DECAPOD CKUSTACEA OP ENGLAND. ■ 31 



lobes by two notches in the upper and one in the lower portion. A 

 specimen in my collection has an elongated ophthalmic peduncle 

 •divided by slender longitudinal ridges into three or four spaces, 

 in one of which numerous minute corneal facets are distinctly 

 visible. Pterygostomate regions steeply inclined aud minutely 

 granulated. 



Bell's figure represents the marginal orbital lobes as pointed, but 

 in a well-preserved specimen in my collection these processes exist 

 as flattened, quadrate lobes, separated by distinct parallel-sided 

 fissures. 



Distribution. — London Clay. Specimens are in the "Woodwardian 

 and Malton Museums, and my own collection, etc. Derivative 

 examples occasionally occur in the Crag. 



Genus Mitheacia, Eell. 



MlIHKACIA LTBINIOIDES, Bell. (PI. II, fig. 8.) 

 1858. Bell, Monogr. pt. i, p. 9 & pi. v, figs. 10-12. 



Supplementary. — The inflated lobes which occupy the lateral 

 portions of the scapular area represent the confluent meso- and 

 metabranchials. Two slight eminences occur between the cardiac 

 lobe and the posterior border of the carapace. The characters of 

 the limbs have yet to be ascertained. 



Affinities. — This species is readily distinguishable by the semi- 

 globose form of the carapace, and by the sharp definition and in- 

 flation of the principal dorsal lobes. The surface-granules are 

 unusually prominent. 



Mitliracia is probably represented in foreign Tertiaries by the 

 genus Micromaia, Bittner. There is a general resemblance in the 

 character of the carapace of these genera, but they differ in the 

 conformation of tlie orbito -frontal region, the rostrum of Micromaia 

 being prominent and widely bifid. 



Distribution. — Of this rather rare species there are eight specimens 

 in the British Museum and two in the Woodwardian Museum, all 

 from the London Clay of Sheppey. 



MiTHRACIA OBLITA, Sp. nOV. (PI. II, fig. 4.) 



Description, — Carapace broadly ovoid in outline, rather longer 

 than wide, highly vaulted transversely, strongly deflexed in front, 

 nostrum small, entire. Orbito-frontal border equal to two-thirds 

 the length of the carapace. Posterior border slightly wider than 

 the orbito-frontal. A sharp cervical sulcus indents the antero- 

 lateral border, crosses the carapace, and marks off" the cephalic 

 region, which occupies scarcely the anterior third of the dorsal 

 area, and is rendered nodular by the prominent gastric lobes. The 

 two nodules near the base of the rostrum represent the epigastric 

 lobes ; a small tubercle intervenes between the epigastric aud the 

 orbit ; three nodules occur upon the mesogastric, and one on each 

 metagastric ; the hepatic lobe is very small ; the urogastric is 



