404 EEV. A. M. NOEMAN AND ME. G. S. BEADY 



1861. Ifonospilus dispar, G. 0. Sars. Om de i Omegnen af 

 Christ, forkom. Cladocerer, p. 23. 



Carapace obovate or subrotund, wider in front than behind, 

 dorsal margin very much arched ; posterior margin subtrancate ; 

 ventral convex; infero-posteal angle completely rounded off; 

 valves composed of many plates overlapping each other, the 

 smallest not half the size of the largest,* the ventral margin of 

 each of these plates ciliated, head and dorsal portion of carapace 

 rugose, curiously sculptured with sunken pits. Head depressed, 

 very shallow and small, rostrum produced, pointed ; compound 

 eye wholly absent ; eye-spot present in the usual position at the 

 origin of the anterior antennae, which are shorter than the ros- 

 trum. Posterior antennae of moderate length, an unusually large 

 and conspicuous spine at the distal extremity of the branch which 

 bears three setae only ; and both branches having the terminal 

 setae accompanied by a similar but smaller spine. Abdomen 

 short and very deep, superior margin swelling out just beyond 

 the abdominal setae, and subsequently hollowed out nearer to the 

 widely truncate extremity ; furnished with articulated spines 

 varying greatly in size (mostly very minute), and irregularly 

 disposed both on the edge and the sides, and extending quite 

 round the supero-posteal angle, which is completely rounded off ; 

 the largest spines are about this angle ; terminal claws very 

 powerful, and furnished at their base with a large spine, which 

 is half as long as the claw itself. Length, -rb-th of an inch. 



* In a gathering of Entomostraca from Crag Lough, A. M. N. has found a very consider- 

 able number of specimens of Lynceus elongatus, in which the carapace consisted of a series of 

 valves lying one over another. It appeared as though the animal, instead of undergoing its 

 usual periodical exuviations, retained the older valves outside the more recently developed 

 envelopes. It is however a puzzling matter for speculation, why the particular examples of 

 L. elongatus referred to did not undergo the usual sloughings. Was it that they were in a 

 diseased state, and had not strength to cast their skins ? We scarcely think that this can 

 have been the cause, for, if so, it seems improbable that they would have lived, labouring 

 under disease, during the length of time which, the uncast carapaces indicated. The state 

 of these specimens differed from that which is usual in Monosjrilus tenuirostris in one par- 

 ticular, viz., that while in the former, the carapaces being all of nearly the same size, show 

 that their retention had not commenced until the animal was fully grown, in the latter 

 the small size of the outermost of the coverings, and the gradually increasing dimensions 

 to the innermost, prove that the skin has not been cast during a considerable period of the 

 animal's growth. 



