383 



expansion covering the bases of the superior antennae, lateral corners obsolete. 

 Coxal plates not very deep, sometimes very small. Last pair of epimeral 

 plates much narrower, and also less deep, than the preceding pairs. Eyes distinct 

 or imperfectly developed. Antennae very unequal, the superior ones being 

 much the larger, and having no accessory appendage. Oral parts somewhat 

 differing in the various genera. Gnathopoda small, simple, or with an ap- 

 proach to a subcheliform character. Pereiopoda more or less powerfully 

 developed, with hook-like dactylus, basal joint of the 3 posterior pairs lami- 

 narly expanded. Last pair of uropoda more or less differing from the preceding 

 pairs. Telson squamiform, entire. Sexual difference very slight. 



Remark*. I have found it necessary to establish this new family 

 in order to include the very anomalous genus LapTiystius of Kroyer, which, 

 in my opinion, was wrongly referred by Boeck to the Ipliimedidce, differing, 

 as it does, rather markedly both in external appearance and in several 

 anatomical characteristics. To this genus is now for the first time added 

 another very remarkable genus, LapTiystiopsis, which exhibits several charac- 

 teristics in common with Laplnjstlus, from which in other particulars it differs 

 rather strikingly. 



Gen. 1, Lapbystius, Kroyer, 1842. 



Syn. : Darwinia, Sp. Bate. 

 ,, Ichthyomyzocus, Hesse. 



Body distinctly depressed, with the back evenly vaulted throughout. 

 Cephalon rather broad in its posterior part, and having the rostral expansion 

 somewhat tapering distally. The 3 anterior pairs of coxal plates of normal 

 appearance; 4th pair much deeper than the preceding pairs; the 2 succeeding 

 ones with the posterior lobe produced below. Eyes distinct, prominent. Su- 

 perior antennae of moderate length and very strongly built, with the flagellum 

 only composed of a limited number of articulations. Buccal area rather 

 projecting below. Anterior lip tapering distally to an obtuse point; posterior 

 lip rather large and without any inner lobes. Mandibles very strong, with, 

 the cutting part prolonged and exserted to a narrow, strongly-dentated plate, 

 inside which there is a secondary lamella differently shaped in the two 

 mandibles, molar expansion wanting, palp very large. First pair of maxillae 

 with the palp quite rudimentary, nodiform, basal lobe not very large, trise- 

 tose. Second pair of maxillae with the outer lobe considerably larger than 

 the inner. Maxillipeds short and broad, laminar, basal lobes narrow, masti- 

 catory lobes very large, palp extremely small, biarticulate. Gnathopoda 

 rather unequal in structure, the anterior ones being very feeble and simple, 



