A HISTORY OF WARWICKSHIRE 



names. In particular the species L. quadrangularis was transferred in 

 1843 by Dr. Baird to a new genus, Alona. Baird indulged in the incon- 

 sistency of retaining the family Lynceidas, although he left in it no genus 

 Lynceus. Mr. Hodgson and some other authorities have avoided this 

 fault by retaining the genus Lynceus in place of Alona. But Lynceus 

 cannot be in two places at once. Being a phyllopod, it cannot likewise 

 be a cladoceran. For several of the genera in this family Baird notices 

 something distinctive in the external form. Thus, Cbydorus, Leach, is 

 ' nearly spherical in shape ' ; Acroperus, Baird, ' somewhat harp-shaped ' ; 

 Alona, ' quadrangular' ; Eurycercus, Baird, ' sub-quadrangular' ; Camp- 

 tocerus, Baird, and Peracantha, Baird, respectively 'ovoid' and 'oval'; 

 while Pleuroxus, Baird, has the lower part of the ventral margin ' trun- 

 cated, or, as it were, cut sharp and straight.' He contrasts the motion 

 through the water of Alona quadrangularis with that of the Daphniidae, 

 for ' instead of swimming by short irregular bounds, as these latter do, 

 they direct themselves by a rapid motion of their inferior antennae, or 

 rami, and legs, straight towards the point to which they wish to go.' ' 

 He considers that this probably depends on the shortness of the branches 

 of the second antennas, since among the species of another family 

 Bosmina longirostris, which also has very short branches similarly situ- 

 ated, has the same kind of motion. As in the Daphniidas, so in the 

 Chydoridas, the eye, Baird observes, ' is a spherical body contained in 

 a somewhat funnel-shaped sheath of muscles, having a semi-rotatory 

 motion, and consisting of a series of crystalline bodies, which, in the 

 Eurycercus lamellatus, are about twenty in number.' 2 In Eurycercus 

 Dr. Jules Richard notes that the optic ganglia and their nerves are 

 clearly separated one from the other, though all the same the eye 

 remains single, 3 thus strengthening the recognized probability that the 

 single eye of the Cladocera has arisen from the fusion of eyes originally 

 paired. 



Passing on to the Gymnomera, we find this section likewise divided 

 into two tribes, the Onychopoda with four pairs of feet, nail-bearing feet 

 as the name implies, and the Haplopoda, with six pairs of feet, these 

 being in accord with the name simple, unarmed. The so-called nails 

 of the Onychopoda are supplied by unguiform setae. In this tribe the 

 family Polyphemidas supplies Warwickshire with the interesting species 

 Polyphemus pediculus, de Geer. Mr. Hodgson describes its distribution 

 as ' local : Olton Mill Pool ; Blackroot, Sutton.' In the second tribe 

 the family Leptodoridas supplies Leptodora hyalina, Lilljeborg, ' abundant, 

 canals and some large pools.' This species was recorded in 1879 from 

 ' a pool in the neighbourhood of Olton ' 4 by Mr. Walter Graham, 

 F.R.M.S., President of the Birmingham Natural History and Micro- 

 scopical Society, his identification of it being corroborated by Professor 

 Ray Lankester. Lilljeborg now accepts L. kindtii (Focke) as its right 

 name. 



1 British Entomostraca, p. 122. * Loc. cit. p. 117. 



* Ann. Set. Nat. ser. 7, vol. xviii. p. 312. * The Midland NaturaSst, ii. p. 225, pi. 5 (1879). 



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