D. J. SCOUKFIELD ON THE WINTER EGG OF A RARE WATER-FLEA. 177 



were seen, or something to that effect. Professor Sars says that 

 it has never been taken in Norway (8, p. 19), which in itself 

 speaks much in favour of the idea that it is really a rare form, 

 at least in Europe. It is just possible that this is the first time 

 that it has been recorded in this country, for although Norman 

 and Brady in their " Monograph of the British Entomostraca," 

 (5,) mention a species which they refer toL. acanthocercoides, it is 

 more likely that they actually had before them our commoner 

 species Z. quadrangularis. The latter species I have myself, in 

 papers published before 1898, recorded as L. acanthocercoides, but 

 that was done under the impression that the two forms were 

 not distinct species. I do not now think there can be any reason- 

 able doubt as to their distinctness, and it may be useful to other 

 collectors in this country if I give the chief points which I rely 

 upon for identification, 



Leydigia ACANTHOCERCOIDES, Fischer. Shell marked with more 

 or less evident longitudinal ribs, and also with extremely fine 

 longitudinal striae. Terminal claws without a tooth at the base. 

 Dorsal margin of body, between anus and abdominal setee, mth 

 three or four little notches. 



Leydigia quadrangularis, Leydig. Shell without evident 

 markings of any sort. Terminal claws with a small but distinct 

 tooth at the base. Dorsal margin of body between anus and 

 abdominal setse without notches. 



Fischer, in his original description of his Lynceiis acanthocercoides 

 (1, p. 431), specially refers to the extremely fine striae between the 

 coarser markings, and the presence or absence of this character 

 seems to furnish an important means of separating the two 

 species. My specimens of L. acanthocercoides have all exhibited 

 these fine striae, while I have never seen a trace of such striae 

 in L. quadrangularis. The presence of the little notches or 

 crenations between the anus and the abdominal setae is also, I 

 believe, characteristic of L. acanthocercoides, although it has not 

 previously been noticed. The dorsal margin in this region is 

 quite unbroken in L. quadrangularis, (see Leydig (4) Taf. viii. 

 fig. 59). It must be mentioned, however, that Sars has described 

 a form from South Africa (8, p. 18), referred to L, acanthocercoides, 

 which does not apparently exhibit the extremely fine striae, at 

 least they are not specially alluded to, nor does the dorsal margin 

 of the body between the anus and the two long abdominal setae 



