1863.] WOODWARD MACKTTKOTTS CRUSTACEAN. 319 



found in the Oxfordian Oolite of Normandy *, and those occurring 

 in the Inferior Oolite f and Lower Lias t of Bavaria. 



After careful comparison, I am satisfied that our Liassic Crustacean 

 is quite distinct from any of these. 



Scapheus, gen. nov. 



The carapace of Scapheus differs from the nearly smooth cephalo- 

 thorax of Megacheirus, which is quite destitute of the spines and 

 prominent rostrum so conspicuous in this fossil ; and the smooth, 

 slender fore-limbs of Megacheirus (considerably exceeding the entire 

 length of the body) contrast strongly with the more robust spiny 

 arms and great terminal hooks of Scapheus. In the basal joints of 

 the outer antennae, the form of the abdominal segments, and the 

 laminse of the tail, this new genus is also distinguished by well- 

 defined characters. I propose to name the only known species, re- 

 presented by Mr. Harrison's specimen, Scapheus ancylochelis §. 



The long monodactylous fore -limbs are quite peculiar to these 

 fossil genera of Crustacea. The nearest living analogues are found in 

 the fossorial group Thalassinidce, but the resemblance is only evident 

 in the structure of the limbs and in the hirsute character of both 

 limbs and abdomen ; the termination of the fore- arms in Scapheus 

 being similar to Ranina, another burrowing Crustacean of a different 

 group. The abdomen, however, in nearly all the true fossorial 

 species is more or less rudimentary, and but little adapted for nata- 

 tion, whereas in this genus the marginal (or epimeral) portion of 

 the abdominal segments is as well developed as in Nephrops or 

 Homarus ; and the laminae of the tail and the traces of false ab- 

 dominal feet also indicate a Crustacean well adapted for swimming. 

 Taking these points of structure into consideration, we cannot sup- 

 pose this to have been an habitual burrower, but simply as searching 

 for its food and concealing itself among stones, for moving which its 

 powerful fore-limbs seem well adapted, although (from the very 

 rudimentary character of the fixed ramus of the penultimate joints) 

 but little suited for organs of prehension. 



The great similarity of the Crustacea of our English Lias with 

 those from Solenhofen has appeared to me to be a most interesting 

 point, and I hope hereafter to offer figures and descriptions of several 

 others not yet enumerated from our Lias, and all analogous to those 

 of the Upper White Jura of Bavaria. 



Scapheus ancylochelis, spec. nov. 

 Cephalo thorax one -third longer than deep. Eostrum prominent, 



* Palaeontographica, vol. i. p. 144. t. 19. f. 2-19. 



t Der Jura, p. 520. t. 69. f. 8-11. This species, described by H. von Meyer 

 under the name of Eumorphia socialis, from Dives in Normandy, &c, is the same 

 which Quenstedt describes as Mecocheirus socialis, from the Inferior Oolite of 

 Bavaria. It is much smaller than M. longimanus from the Solenhofen limestone. 



\ Quenstedt describes two species from the Lower Lias of Bavaria — Meco- 

 cheirus grandis, Q. (p. 88. t. 11. f. 15, 16), and M. olifex, Q. (p. 89. t. 11. f. 17). I 

 consider M. grandis more nearly related to our Lias genus than to Megacheirus, 

 so far as Quenstedt' s figures permit me to judge. 



§ From <TKa<pevs, a " digger," and ayicv\oxrjhr}s, "with hooked claws." 



