496 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 23, 



The sides of the carapace curve rapidly inwards in front, leaving 

 the anterior margin only half the width of the posterior portion. 



The carapace is broadly notched in front with two lateral orbital 

 fossae formed by the lateral angles of the carapace. 



A tuberculated ridge passes up the centre of the carapace, from 

 the posterior margin to the cervical furrow, by which it is inter- 

 sected ; it reappears for a short space in front. 



Two lateral equidistant tuberculated ridges mark out the branchial 

 regions, and are also continued smoothly upon the frontal portion of 

 the carapace. 



Each antenna of the inner pair has two many-jointed setae, the 

 outer one being slightly the longer. Each of the outer antennae 

 has a large oval scale attached to its broad basal joint ; the setae are 

 single, and scarcely thicker than those of the inner pair. 



The eyes, but rarely preserved, are placed near the base of the 

 scale of the outer antennae. In a specimen from Lyme Eegis (from 

 Mr. Day's collection, and now in the British Museum) the external 

 pair of footjaws (or sixth pair of maxillary appendages), with their 

 broad oblong basal joints and their more slender four-jointed palpi, 

 are well preserved. 



The first pair of legs are robust and short, as compared with 

 Eryon antiquus, the hand and carpus nearly equalling the length of 

 the middle of the carapace ; fingers slender, pointed, of equal length, 

 incurved at the tip, the moveable one most incurved. 



The succeeding pairs of feet are much smaller, and are each ter- 

 minated with pincers, except the fifth pair, which are monodactylous 

 at their extremities. The abdomen is slightly longer than the cara- 

 pace, and one-third less in width ; the first segment is narrow, and 

 has two tubercles on its lateral margins; the second, third, and 

 fourth have each two lateral and a median tubercle ; the sixth seg- 

 ment has a median and two lateral ridges ; these are continued on 

 the seventh segment or *'telson," which is acutely triangular in 

 form; the caudal plates are very broad, and roundly quadrate in 

 form ; the outer pair of plates are divided by a curved suture near 

 their extremities as in other Astacidce*. 



The epimera of the first five segments are rounded ; that of the 

 sixth is falcate, and to its lateral and posterior margins the caudal 

 lamellae are articulated. 



Dimensions (from a specimen in the British Museum). — ^Length 

 4| inches ; extreme breadth of carapace 2 inches 4 lines ; length 

 of carapace 2 inches 2 lines ; breadth of frontal portion of carapace 

 1 inch ; length of abdomen 2 inches 8 lines, breadth of same IJ 

 inch ; breadth of caudal plates 2 inches 4 lines ; extreme length 

 of chelae 2 inches 10 lines (length of second pair of limbs 2 inches 

 4 lines, Mr. Brodie's specimen); breadth of first pair of limbs 3 

 lines, second pair 2 lines. 



Localities. — Lias, Barrow-on-Soar. 



The affinities of this species are more with Eryon antiquus, save 



* This suture is absent in the outer caudal lamellae of the Solenhofen species 

 — a most important distinction : they differ widely also in form. 



