136 Transactions of the Society. 



differs remarkably in habit from the other species of the genus, 

 which we have found almost in any quantity at each gathering. 



Gosse's weak description of this rotifer makes it difficult to 

 identify, but as he likens it to D. gracilis, we feel sure we have 

 the species he described. 



The jaws are certainly very like those of gracilis, except that 

 the incus has a blunt broadish end, whereas in gracilis it ends in a 

 point. 



The hyaline appearance of the body, the width of the lateral 

 cleft, the straight toes, and the want of pigmented eye, are suffi- 

 cient to distinguish this easily from other Diaschizse. 



The body is almost cylindrical, very slightly gibbous, and 

 showing just the least trace of lateral compression. 



The venter is narrower than the dorsum. 



The head, which is of the same width as the body, carries a 

 ring or collar surrounding the corona, especially noticeable on the 

 dorsal side, the extreme dorsal point projecting abruptly forward. 



The face is sub-prone. The buccal orifice slightly protrudes. 

 Above this is situated a bunch of stiff setse. 



Every example of this species which we have found has so far 

 had a transparent lens on the lower part of a large brain-sac ; but 

 we do not consider this to be an essential mark of the species, as 

 we have known it to vary exceedingly in size. 



The stiffened integument ends abruptly a considerable distance 

 in front of the base of the toes, which makes it difficult to deter- 

 mine foot from trunk. This, as already mentioned, is to some 

 extent common to the whole genus, but is abnormally marked in 

 this species. 



The setse on the foot are very long. 



The toes are thin rods, and almost straight, the dorsal edge 

 quite straight, the ventral tapering very slightly in an upward 

 curve, and so producing, with the dorsal edge, a very sharp point. 

 They are not wide apart at the base, nor so blade-shaped as in 

 D. cceca. They are often thrown up over the back. 



The stonmch is sometimes tinted with food, but the whole 

 animal has a remarkably hyaline appearance, which is one of the 

 first features to strike one's notice. 



EXPLANATION OF PLATE IV. 



All figs, x 476. 



■»■- 



Fig. 11 — Diatchita casca Gosse. Lateral view. 



„ 11a „ „ „ Dorsal view. 



„ 12 „ te)tuior Gosse. Lateral view. 



„ 13 „ Derbyi sp. n. Dixon-Nuttall and Freeman. Lateral view. 



„ 13a ,, „ „ „ Lateral view. 



„ 136 „ „ „ „ Dorsal view. 



„ 14 „ ? megcdocephala Gla»cott. Lateral view. 



., 14a „ „ „ Dorsal view. 



