different genera. Eye, when present, exhibiting 3 highly refracting lenses, one 

 ventral and 2 lateral, imbedded in a dark pigment. Anterior antennae, unlike 

 what is generally the case in Copepoda, extended straight forwards, and composed 

 of a limited number of joints clothed with rather unequal setae pointing in 

 different directions, some of them being much elongated and finely ciliated, 

 some others, attached to the terminal joint, exhibiting not seldom a peculiar 

 dichotomous ramification ; same antennae in male distinctly hinged. Natatory 

 legs present in the usual number, and very powerfully developed, with 

 the basal part large and muscular and both rami 3-articulate. Last pair 

 of legs in female represented on each side by a single more or less lamellar 

 joint carrying a restricted number of plumose setae; in male much reduced, or 

 wholly absent. Alimentary canal quite obliterated. Ovaria, when fully developed, 

 very massive, filling up the greater part of the body-cavity and extending 

 anteriorly within the frontal part of the head; the ripe ova not included in 

 any true ovisacs, but agglutinated to 2 slender juxtaposed spines or filaments 

 issuing from the ventral face of the genital segment, these spines being in 

 male replaced by a thickish, somewhat clavate appendage, into which the . 

 spermatophores are received before extrusion. 



Remarks. Of this family at first only 2 species were known, derived 

 from 2 widely remote localities, the one recorded by Dana from the Sulu Sea 

 as Monstrilla viridis, the other by Kr0yer from thn Norwegian coast as 

 Thaumaleus lypictis. These 2 species, though bearing very different names, 

 are evidently nearly allied, and were also by most subsequent authors regarded 

 as congeneric. In more recent times a considerable number of additional 

 forms of the same remarkable type have been recorded from different 

 parts of the oceans, and it appeared desiderable to group these species 

 according to some more conspicuous diversities found between them. 

 Thereby the first step to a subdivision of the genus Monstrilla was intimated. 

 Such a subdivision was indeed carried out in the year 1892 by Giesbrecht, 

 who referred the Monstrillidae at that time known to 2 nearly-allied genera, 

 chiefly characterised by the segmentation of the tail and by the number of 

 the caudal setae. For the one of these genera he retained the old name 

 Monstrilla, for the other he applied the name Thaumaleus proposed by Kr0yer, 

 and this arrangement has now generally been admitted by carcinologists. I am 

 also of opinion that these 2 genera should be supported ; but I am by no 

 means prepared to consent with Giesbrecht in his application of the name 

 Thaumaleus to the one of these genera. For it is quite certain, that the form 

 recorded by Kr0yer is not referable to Giesbrecht's genus, differing as it does, 



