1909.] ON ASIATIC FISHES OF THE FAMILY AXABANTID^. 767 



To sum up shortly the result of this induction. It seems fairly 

 proved that Mya arenaria, one of the very commonest shells in 

 the present seas of Scandinavia, Britain, and Belgium, where the 

 conditions are singularly favourable for it, has only recently invaded 

 those shores. Secondly, that it is not an Arctic shell as has 

 been supposed, but a boreal one. It has not been found living in 

 Arctic waters, and its alleged occurrence there has been due to a 

 mistaken inference. Hence, all deductions as to glacial climate 

 deduced from its having occurred in certain beds must fall to the 

 ground. It may well be, as Brogger suggests, that when it 

 recently invaded the European seas it came from North America. 

 On the other hand, the same shell existed abundantly in Britain in 

 the times of the Middle and Later Crag, and has been found in 

 Scandinavia at Uddevalla, affording some evidence that a portion 

 at all events of the Uddevalla shell-beds are what is called pre- 

 glacial or late Crag. So that the mollusc must have died out for 

 a considerable time or been exterminated. Meanwhile it becomes 

 a very good test to discriminate between the shells of the Crag 

 and those derived from it, on the one hand, and the subsequent 

 fauna of the raised beaches etc., down to recent times, on the other. 

 The cause of its extinction and the explanation of its reintro- 

 duction, unless the latter was due to hviman agency, are equally 

 puzzling. The notion that Mya arenaria was the victim of that 

 Deus ex macMna, the Ice KgQ^ is excluded by the fact that the 

 companions of this shell in our modern estuaries suffered no such 

 extinction, but survived all through the period from the Crag 

 age until our own day. 



2. The Asiatic Fishes o£ the Family Anahantidae. 

 By C. Tate Began, M.A., F.Z.S."^ 



[Received September 27, 1909.] 



(Plates LXXVII.-LXXIX.t) 



In my classification of the Teleostean Fishes (Ann. Mag. N. H. 

 (8) iii. 1909, pp. 75-86), the Anabantoidei are placed as a sub- 

 order of the order Labyrinthici, which includes also the Ophio- 

 cephaloidei. 



The Labyrinthici foi-m a terminal group which has attained a 

 considerable degree of specialization ; they are physoclistie, the 

 parietal bones ai'e separated by the supraoccipital, there is no 

 orbitosphenoid, the protractile prfemaxillaries exclude the tooth- 

 less maxillaries from the oral border, there is no mesocoracoid, the 

 vertebral centra are solid and coossified with the arches, and the 

 pelvic fins are placed well forward. Characteristic is the presence 

 on each side of a supra-branchial cavity which contains a laminar 



* Communicated by permission of the Trustees of the British Museum. 

 f For explanation of the Plates see p. 787. 



