322 



Canada, is the half of a nodule containing an Astacidean from the 

 Upper Cretaceous of the north-east side of Hornby Island, British 

 Columbia, collected by J. B. Bennett in 1898 (No. 55D). 



"The Crustacean is seen in profile on the split surface of a nodule, and 

 exhibits the cephalothorax, with its stout pair of chelate limbs (or forceps) 

 attached, and the remains of the four pairs of succeeding ambulatory legs, 

 the six abdominal somites, and the telson, but the lateral lobe of the tail- 

 fin was probably preserved in the other half of the nodule not sent. The 

 branchiostegite (covering the branchiae) is broad and tumid, and the 

 branchiocardiac groove is strongly marked. Starting from the median 

 dorsal line as a V-shaped furrow, about 12 millimetres from the posterior 

 border, it bends rapidly forward, becoming deeper on each side, and 

 reaches the lateral border 24 mm. in advance ; here it unites, close to the 

 hepatic lobe, with the equally deep but more transverse cervical furrow, 

 which crosses the carapace 10 mm. i earer to the front. In advance of 

 the cervical groove the postorbital ridge and spine can be seen, also the 

 base of one of the antennules, with part of one of its flagella, beneath the 

 somewhat short rostrum, and lower down the base of one of the outer and 

 larger antenna^. The surface of the branchiostegite is marked by numerous 

 small tubercles scattei'ed irregularly over the surface. The branchial, 

 cardiac, and hepatic regions are also similarly tuberculated, and very 

 tumid. Length of carapace 48 mm., depth of side 25 mm. The ambu- 

 latory limbs are fairly long and slender ; the chelate limbs measure about 

 60 mm. in length ; length of penultimate joint 35 mm., breadth 15 mm., 

 length of ultimate joint 20 mm. The fingers are long and slender, the 

 inner edge of the forceps being denticulated ; wrist 6 mm. long by 10 

 mm. broad. The epimeral border of each abdominal segment is falcate 

 in contour. 



" The general form and details of this Crustacean, so far as preserved, 

 clearly mark its place among the Astacidea, or under the Astacomorpha 

 (as defined by Huxley, 1881), and I would suggest that Oppsl's name of 

 Eryma is appropriate for it, seeing that it agrees very closely in the 

 divisions of its carapace and its tuberculated surface, in the antennae, the 

 form of the first pair of forcipated chelae, and the proportion of its abdo- 

 men, with E. Perroni and other Jurassic species. 



" Oppel observes that no examples of the genus Eryma have been found 

 in rocks younger than the Jurassic, and that the Astacidse of the Chalk 

 are placed in McCoy's genera Hoploparia and Enoplodytia, but in this 

 instance the form in question agrees much more closely with Oppel's genus 

 Eryma than with other forms. I therefore propose to relegate it to that 

 genus, and to designate it by the specific name of Daivsoni, in honour of 

 Dr. G. M. Dawson, C.M.G., F.R.S., the eminent Director of the Geological 



