CRUSTACEANS 



attained by the common prawn, is certainly very unusual for the Pala- 

 monetes. Like the eels entrapped in the pits at Rome, it may in an 

 unusual situation attain an unusual size. It may find congenial food 

 and be free from harassing foes. That condition of things helps one 

 to grow fat. As to the incidental sarcasm on the paucity of north 

 Norfolk naturalists, it may in itself have been well deserved, but there 

 is no coast far or near on which naturalists can hope to compete in 

 numbers with the prolific prawn. Mr. Skertchly's own argument is 

 invalidated by one startling inconsistency, since he first affirms that 'the 

 ova are carried by the females until they hatch,' and presently after- 

 wards sums up in favour of a supposition that the ova had been buried 

 in the silt and lain dormant for an enormous period. He can scarcely 

 intend that they were buried with the parent and survived the unpleas- 

 ing contiguity of her decay. He speaks also of the silt affording plenty 

 of water for their preservation. But it is, I believe, the fact that crus- 

 tacean ova which are known to retain vitality for a long time without 

 hatching out belong exclusively to the Entomostraca, and that they are 

 preserved in dried mud, not in moist. The hfe history of such species 

 has been adapted to their residence in water-basins which are liable to 

 complete evaporation, to be followed by replenishing at a future season. 

 No such expedient could be necessary for the prawn. But, where 

 strong springs can rise in a pit, there seems to be no reason why the 

 tiny larval prawns should not be carried safely along with the water. 

 At any rate, the survival of malacostracan eggs during thousands of years 

 cannot be accepted on existing evidence. 



Nearly related to the shrimps and prawns in appearance, and per- 

 haps also in fact, are the Schizopoda, the order of the cloven feet. 

 They are so called because many of their legs have two branches. But 

 this is the case also with lobsters and many other crustaceans in their 

 juvenile stages ; and a few of the Macrura retain the second branch even 

 in adult life. In the pleon, moreover, double-branched appendages are 

 rather the rule than the exception. Of schizopods, Norfolk has at least 

 one on record — the pretty and delicate, black-eyed, almost transparent 

 Gastrosaccus spinifer (Goes). The hind margin of its carapace forms 

 an elegant curve, fringed within by eight acute denticles.^ 



Of the sessile-eyed Malacostraca, I have in my possession a speci- 

 men of the isopod Astacilla longicornis (Sowerby), taken off Yarmouth by 

 Dr. G. S. Brady, F.R.S., by whom also the schizopod just mentioned 

 was obtained. Of the Isopoda, it may suffice here to remark that the 

 county is sure to yield by land and water a long list of species to any 

 naturalist who will, with moderate diligence, search for them. Of 

 another sessile-eyed group, the Amphipoda, much the same may be said. 

 Of these, Metzger's catalogue contains the following names : Dryope 

 crenatipalmata. Bate; Noeriia excavata. Bate; Aora gracilis. Bate; Mtcro- 

 deutopus anomalus, Rathke ; Ampelisca tenuicornis Lilljeborg ; Melita obtusata 



1 A. M. Norman, in Brithh Association Report for 1 868, p. 268 ; Stebbing, in Annah 

 and Magazine of Natural History for August and October, 1880. 



191 



