ASTACODES. 31 



generic distinction from all other forms hitherto discovered. The examination of a beautiful 

 specimen of the last five segments of the abdomen, with the caudal appendages, formerly in 

 the collection of Mr. Bean, of Scarborough, and now in the British Museum, and of several 

 fragments in the museum at York, for the loan of which I have to acknowledge the cour- 

 tesy of the council of that institution, has enabled me to arrive at the conclusion above 

 stated. The carapace is large and rounded, everywhere coarsely granulated, the granula- 

 tions being more rough and less frequent on the anterior portion ; the nuchal furrow deep 

 and sloping, bordered on each side by a small, granulated carina, and there are two or three 

 longitudinal carinas on the sides of the anterior part of the carapace ; the abdomen is semi- 

 cylindrical, very even, polished, and conspicuously punctate; the epimeral plates of the 

 fourth, fifth, and sixth segments are prolonged into an elegant falciform process, with the 

 points directed backwards, and the anterior margin of each regularly dentated. The seventh 

 segment or central caudal plate is broad, and furnished with a few tubercles ; the lateral 

 caudal plates rather narrow, obsoletely carinated, and fimbriated at the extremity ; the 

 common basal point oval ; the hand is remarkably robust, coarsely granulated, the fingers 

 armed with strong tubercles on the prehensile edge. 



Found m the Speeton Clay. 



It appears that Prof. Phillips considers this species as belonging to the genus Meyeria ; 

 it does not, however, appear to me that this view is borne out by the structures above men- 

 tioned. The peculiar characters of that genus are wanting, and the whole aspect of the 

 portions which have come under my observation is widely different. The even, polished, 

 punctate abdomen, with its falciform lateral processes, and the robust, powerful claw, are 

 utterly unlike those parts in the genus in question. 



There is in the British Museum a fragment consisting of three segments of the abdomen 

 of a small macrurous species from the Speeton Clay, formerly in the collection of Mr. Bean, 

 and named by that gentleman Astacus multicavatus. The surface is regularly, as it were, 

 eroded by numerous conspicuous, impressed puncta ; there is on each side a prominent 

 carina ; the epimeral processes are acutely triangular, and turned a little backwards. 



There is also a specimen from the same locality of a pair of hands, which probably may 

 have belonged to the same species. They are of equal size and similar form ; evenly rounded, 

 somewhat tumid, nearly oval, being contracted at each extremity ; the fingers are slender ; 

 the surface is minutely but roughly granulated. In both cases the data are too scanty to 

 afford any satisfactory suggestion as to the relation of the species. 



The specimens are figured, somewhat enlarged, at Plate IX, figs. 7, S. 



