2 Mr. E. J. Miers on the Squillidse. 



needed, as no general account of the group has appeared since 

 the publication of the second volume of Milne-Edwards's 'His- 

 toire naturelle des Crustacea' in 1837 ; and since that period 

 numerous species have been described, not a few of which, 

 having been based on characters of insufficient value, are now 

 reduced to the rank of synonyma. In Milne-Edwards's work 

 the number of distinct species does not exceed twenty ; in the 

 present revision fifty -three species are enumerated, distributed 

 into six genera. 



Milne-Edwards, in 1837, enumerated three genera, Squilla, 

 Coronis, and Gonodactylus, and divided the genus Squilla 

 into two sections of subgeneric value, to include respectively 

 the " Squilles Jines-tailles " and " Squilles trapues." Dana, 

 in 1852*, established the genus Pseudosquilla for Milne- 

 Edwards's " Squilles trajnces," and Lysiosquilla for the first 

 section of his " Squilles Jines-tailles.'''' De Haanf, on the other 

 hand, only retains the genera Squilla and Gonodactylus, re- 

 uniting with Squilla not only Dana's Lysiosquilla, but also 

 the genus Coronis of Latreille. As regards Coronis, De Haan 

 is undoubtedly right ; for this genus differs from Lysiosquilla 

 only in the dilated and orbiculate appendage of the antepenul- 

 timate joint of the thoracic limbs ; and to the fact, already ob- 

 served by De Haan, that in young Lysiosquilla niaculata 

 the form of this appendage approaches that of Coronis, I may 

 add that, in a species (L. Brazieri) described below, the ap- 

 pendages of the fifth and sixth thoracic limbs are dilated as 

 in Coronis, and those of the seventh pair linear and styliform 

 as in the typical Lysiosquilla, and thus a complete transition 

 is established from the one genus to the other. 



In the present revision, the species of Squillidas are distri- 

 buted into six genera, the characters of which may be tabu- 

 lated as follows : — 



I. Ophthalmic segment greatly elongated ; ros- 



trum not reaching beyond half the length of 



this segment Leptosquilla. 



II. Rostrum reaching to the end of the oph- 



thalmic segment. 

 1. Dactyli of the raptorial limbs not dilated at 

 base. 

 Carapace not costate. Postabdomen loosely 

 articulated and depressed ; terminal 

 segment transverse, marginal spines 

 small. Eye-peduncles usually dilated 

 at the distal end Lysiosquilla. 



* Crust, U.S. Explor. Expedition, xiii. p. 615 (1852). 

 t Crust, in v. Siebold's Fauna Japonica, p. 220 (1849). 



