134 FRANCIS H. HERRICK. 



be compared in a general way with the remarkable changes 

 which occur in the metamorphosis of the flat-fishes, where the 

 whole body is more or less completely involved. It seems to be 

 confined to the closely allied Homaridse (Hoinarns, Nethrops) t 

 Potamobiidae (Cambants, Astacits) and Parastacidae (Parastacns 

 Astacoides} of Huxley, besides the Paguridae, or hermit crabs, 

 the Galatheidae, 1 or Spanish lobsters (Galathea, Mjiuidd), embrac- 

 ing many deep sea forms, which with a number of smaller fami- 

 lies are often united into the larger division of the Anomura. 

 In all these forms the dactyles of the large claws appear to open 

 inwards, and although in many cases the smaller feet are non- 

 chelate, or the metamorphosis is abbreviated or at present un- 

 known, we may safely assume that their present state has arisen 

 from a primitive condition such as we find illustrated in the first 

 larval stage of Homarns. 



That the modification in question was of very ancient origin 

 does not admit of doubt. It was already perfected in the Ery- 

 moid Crustacea which inhabited the Liassic seas, unless natural- 

 ists are wholly wrong in assuming that these primitive macroura 

 were the ancestors of the modern crayfishes and lobsters. 



According to Huxley 2 forty species of Eryma have been de- 

 scribed from the rocks of the middle Lias up to the Jurassic 

 (Purbeck to Inferior Oolite) formations. In Eryma modestiformis 

 of Oppel, the claws open inwards, and the stalked eyes are 

 relatively very large, as in an adolescent lobster. 3 After the 

 death of such an individual as Oppel depicts the large claws 

 would lie flat as in a dead lobster, but had no previous torsion 

 in the limbs of this species taken place, the relaxed claw should 

 have turned the dactyles outward as it does in crabs. 



It is interesting to find that in the somewhat less primitive 

 Eryoii arc/ifon/iis, from the Jurassic slates of Solenhofen, a very 



1 Kinnaman has figured five species of Galathea, in all of which, excepting G. 

 Andrewsii the large chelte open inwards, so his drawing is doubtless faulty in this 

 respect. See " A Synopsis of the Britannic Spanish Lobsters and Schrimps," Proc. 

 Roy. Irish Acad., Vol. VIII., Dublin, 1862. 



2 " On the Classification and Distribution of the Crayfishes,'' Proc. Zoo!. Soc. 

 London, 1878, and " An Introduction to the Study of Zoology," illustrated by the 

 Crayfish. New York, 1893. 



3 See p. 163 and plate 8, "The American Lobster," Bull. U. S. Fish Commis- 

 sion, Washington, 1895. 



