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 CRUSTACEANS as I found a single specimen, for the first time, last year in Devonshire, but it has not yet been recorded.' ia Lilljeborg accepts his own trlgonellus as a synonym of P. aduncus (Jurine), but distinguishes the latter from the original P. trlgonellus (O.F.M.) and P. uncinatus, Baird, by the character that the tail of the male is in profile narrower than that of the female and only moderately narrowed apically, whereas in the other two species it is broader, although apically strongly narrowed. In P. trigonellus the rostrum of the female points downwards, but in P. uncmatus it has more or less of a forward direction, in the typical form having its end in lateral view directed forward and sometimes upward, so as to be almost hook-like. 89 Between Chydorus globosus, Baird, mentioned only in Mr. Garnar's list, and C. sphaericus (O.F.M.), taken also by Mr. Scourfield, there is the considerable difference of size, the former being on the average nearly twice as long as the latter. Moreover the tail of the female in Baird's species appears in profile elongate and rather narrow, but in the other species it is short and broad. For those' who wish to make a thorough study of these minute but widely distributed, often multitudinous, and in many cases easily captured animals, the elaborate and copiously illus- trated work by the veteran Swedish naturalist, Prof. Wilhelm Lilljeborg, must be considered indispensable. Although by title it refers only to the Cladocera of Sweden, the English student will find it a well-spring of infor- mation as to those of his own country. The Ostracoda agree with the previous group in being small and numerous and diversified. They are also not difficult to capture. But they are in some ways less attractive. Instead of a transparent test, which allows the observer to see, as it were, the wheels of the watch in movement, here the valves are, as a rule, opaque, enabling the animal to shut itself up as in a box, within which all the working parts, head and tail and limbs, are lost to view. Leicestershire has the distinction of having first supplied to science one notable species of this order. It was in the canal at Fleckney that the Rev. A. M. Norman fifty years ago, in August, 1856, discovered Limnicytbere monstrifica. It is described as having the ' valves, as seen from the side, oblong subquadrangular, strongly spinous and tuberculate, extremities boldly rounded, the anterior bearing on each valve a marginal row of about twelve sharp spines.' From Cypris, in which it was originally placed by Norman, Brady transferred it to his Limnicy there, a freshwater genus of the Cytheridae, nearly allied to Cytbere, O.F.M., which is principally marine. It is con- sidered to be a character of the family at large that the animals are incapable of swimming. In regard to this species in particular Dr. Brady remarks that ' the excessively rugged surface of the shell would, indeed, constitute a serious impediment to any rapid movement through the water,' and cites Norman's observation that it made no attempt to swim in the few days during which he kept it alive. 30 In 1889 Brady and Norman record Cypria exsculpta (Fischer), taken by Norman at Kibworth, Leicestershire, and Notodromas monacha (O.F.M.), taken at Gumley. 81 These two, with the six species taken by Mr. Scourfield in this county, belong to the family Cyprididae, which are distinguished from the Cytheridae by several characters. Thus in the former the shell is generally thin and horny, the eyes when present are simple, 30 Trans. Linn. Soc. xxvi, pt. 2, 420 (1868). " Trans. Roy. Dublin Sue. Ser. z, iv, 69, 96. I 105 14
 * In litt. ii Sept. 1906. " Cladocera Sueciae, 539.