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. 



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