132 M..W. Lilljeborg on two remarkable Crustacea 
the occipital to the angle of the mouth (as in C. trimaculatus) } 
a black horseshoe-like collar, with the convexity directed forward ; 
a black line runs from the collar to the tip of the tail, along the 
vertebral series of scales ; a series of roundish black spots, in- 
distinctly edged with white, along each side of the anterior part 
of the trunk. Tail coloured like the body, without black rings. 
Upper labials seven. 
Thirty inches long. Two specimens, from the Fort Pitt Col- 
lection, are in the British Museum. ‘They are said to be from 
British India, locality unknown. : 
P.S.—Elapomorphus mexicanus and Hydrophobus semifasciatus 
(Pl. IX. figs. 1 & 6) are represented twice their natural size. 
Add to the first list Zretanorhinus variabilis, from Cuba, 
which has lately been received through the kindness of Prof. 
Peters. This raises the total number of species in the British 
Museum to 612, which are represented by more than 4100 spe- 
cimens. According to a statement of Prof. A. Duméril (Arch. 
Mus. ix. 1857), the Paris Collection contains 528 species. 
XVI.—An Account of two remarkable Crustacea of the Order 
Cladocera. By W. Litisesore*, 
[Plate VIIJ.] 
Tur two Cladocera which I am about to describe are of so 
remarkable a structure, that I have not thought myself justified 
in delaying their description, as I had previously intended, until 
Thad an opportunity of issuing a continuation of my treatise on 
the Cladocera, Ostracoda, and Copepoda. Both are found in our 
fresh waters, and are widely disseminated. Baron G. C. Ceder- 
strém, to whom, in this branch of knowledge, we are so greatly 
indebted, first drew my attention to the one species, and also 
transmitted to me specimens of the other. The former differs 
so widely from all Cladocera hitherto known as to form a separate 
family ; but the latter belongs to the Polyphemidz, although in 
some respects it strikingly deviates from the other members of 
that family. 
That the former has not previously been noticed may be 
ascribed to the circumstance that it is so transparent as to be 
seen only with difficulty, although it is larger than any other 
Cladocera,—on which account it may well be contained in a glass 
of water without being seen, even with the aid of a lens. The 
other seems to be very rare, and probably has its abode in deep 
water. 
* From ‘ Ofversigt af Kong. Vet. Akad. Forhandl.’ Read May 16, 1860, 
