CRUSTACEANS the valves in Scapholeberis meet in an acute or obtuse process, but that they pass one into the other with a curve in Simosa. li The genus Daphne, as O. F. Miiller first called it, or Dapbnia, the change- ling which has been so long accepted as legitimate, involves many perplexities besides those connected with its generic name. D. pulex is, among all the ' water-fleas,' probably the most familiar. The specific name is due to Linnaeus. Yet authors commonly ascribe it to de Geer, because in this instance they think that Linnaeus did not very precisely know what he was talking about, and that de Geer did. In fact, it requires a practised specialist to criticize to much purpose the specific and varietal names which have clustered round this form and its nearest allies. In Mr. Garnar's list we find given as species Daphnia magna, D. pulex, D. hamata or minebaba, D. obtusa, D. longispina, D. hyalina, D. galeata. Mr. Scourfield remarks that D. minebaba is only a form of D. pulex, and in his own list gives ' D. pulex (pbtusa and proplnqua forms only), D. longispina, D. hyalina (the small galeata form).' He supposes that Mr. Garnar's D. galeata is the form last mentioned. In this view the records of Leicestershire Daphniae will be reduced to four species, which are thus discriminated by Lilljeborg. D. pulex (de Geer) and D. magna, Straus, have the large terminal spines, sometimes called the caudal ungues, pectinate with spinules or spinuliform setae, whereas in D. longispina, O. F. Miiller, and D. hyalina, Leydig, the armature of the ungues is reduced to fine setules or mere cilia. D. magna, which Dr. Brady transfers to a separate genus, Dactylura is distinguished from D. pulex, not only by its generally superior size, but by having the caudal margin of the female strongly sinuate instead of gently undulating. The size is an ineffective guide, since the length of the adult female in the ' great ' species varies between 3-2 and 5'3 mm., and in the typical species between 3-6 and 4*4 mm., the upper limit of the common species thus being much above the lower limit of its supposed superior. D. longispina has the keel of the head interrupted below the eye, and is thus distinguished from D. hyalina, in which the keel is con- tinued without interruption to the apex of the rostrum. 14 For the last species Lilljeborg accepts four sub-species, in three of which, including hyalina, the front part of the head has, at least in the female, a rounded profile, but in D. galeata, Sars, this part is angular, or produced into a process more or less large, acuminate, and helmet-like. 16 The effect of these variations is some- times extremely eccentric, and even comical. Dr. Brady, in 1898, accepts D, galeata as an independent species, and does the same for D. obtusa, Kurz, 1874, but agrees with M.Jules Richard in reducing D. propinqua, Sars, 1895, to a variety of D. obtusa. He institutes the new species D. hamata, but supposes that it may be identical with D. minehaha, Herrick, 1884. For his discussion of these disputed names his own memoir must be consulted. 16 It is worthy of note that D. propinqua, which Mr. Scourfield has found in the waters of this county, was originally described in Norway, not as a Norwegian form, but as bred in that country by Prof. Sars out of dried mud, which he had received from South Africa. For Scapholeberis Mr. Garnar has recorded two species, S. mucronata (O. F. M.) and S. cornuta (Jurine), but the latter, " Cladocera Sueciae, 66. " Trans. Nat. Hist. Northumb. &c. xiii, 240 (1898). 14 Cladocera Sueciae, 69. 15 Ibid. 104. 16 Trans. Nat. Hist. Northumb. xiii, 217-248, pis. 7-10. IOI
