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XXIII. — On the Genus Anaspides and its Affinities with certain Fossil Crustacea. 

 By W. T. Calman, B.Sc., University College, Dundee. Communicated by 

 Professor D'Arcy W. Thompson. (With Two Plates.) 



(Read 18th May 1896.) 



The genus Anaspides was founded in 1894* by Mr G. M. Thomson of Dunedin, 

 New Zealand, for the reception of a very remarkable Schizopod Crustacean which he 

 had discovered in a fresh-water pool at an altitude of 4000 feet on Mount Wellington 

 in Tasmania. The very striking peculiarities of the animal, the absence of a carapace, 

 the presence of plate-like gills attached to the bases of the thoracic legs, and the 

 possession of an auditory organ in the peduncle of the antennules, led its discoverer to 

 regard it as the type of a new family of Schizopods, the Anaspidse, while suggesting 

 that it might be entitled to " even higher specific rank." I have had an opportunity of 

 examining three specimens of Anaspides presented to the Museum of University College, 

 Dundee, by Dr Chas. Chilton of New Zealand, and from the dissection of one of these 

 I have been able to supplement, in some important points, Mr Thomson's account of 

 the external anatomy of the animal. I wish also to call attentiou to the remarkable 

 resemblance, indicative I believe of close affinity, which Anaspides bears to certain 

 Palaeozoic Crustacea belonging to a group hitherto supposed to be unrepresented 

 among living forms. The present paper has been prepared under the direction of 

 Prof. D'Arcy W. Thompson. 



MORPHOLOGY OF ANASPIDES. 



Body. — When Mr Thomson describes Anaspides as possessing eight free thoracic 

 segments, he makes no mention of the extreme interest and importance which would 

 attach to such a state of things. In no living Malacostracan, save Nebalia and certain 

 Stomatopods, do we find more than seven segments of the thorax completely defined, 

 the segment corresponding to the first pair of maxillipeds being fused with the head 

 even where, as in the Edriophthalmata, there is no other trace of a carapace. Mi- 

 Thomson's comparison of the body of Anaspides with that of an Amphipod would not 

 therefore be strictly tenable, since, on his own showing, there is a difference in the 

 number of segments. We believe, however, that this anomaly does not exist, and that 

 Anaspides in this respect forms no exception to the rule among Malacostraca. Careful 

 examination shows that the line which, in Mr Thomson's figure, marks off the "first 



* Trans. Linn. Soc. Zool. (2), vi. 3. A preliminary account, without figures, was published in Proc. Roy. Sec. 

 Tasmania, 1892. 



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