THE SYNC ARID A 169 



be indeed the significance of the " cervical groove ") is not so distinct 

 in any other Euraalacostraca. The homologies of the segments of 

 the endopodite in the thoracic limbs are not quite clear, but the 

 fact that the main flexure of the limb is between the fifth and sixth 

 segments in Anaspides is a point of agreement with the Peracarida, 

 to which group some slight resemblance may be traced in the 

 structure of the maxillae. The possession of a statocyst in the basal 

 segment of the antennule is only paralleled among the Decapoda, and 

 the presence of a receptaculum seminis on the last thoracic sternite 

 of the female and the modification of the first two pairs of pleopods 

 in the male may also point to an affinity with that group. On the 

 other hand, the double series of epipodial lamellae on the thoracic 

 appendages of both genera, and the double gnathobasic lobes on the 

 coxopodite of the first pair in Amispides, are important features not 

 found in any other Malacostraca. 



The fossil genera mentioned above show that already in 

 Palaeozoic times a group of Malacostraca existed which, while 

 retaining caridoid features in tail-fan, antennules, antennae, and 

 pedunculated eyes, had a completely segmented body and no 

 carapace. Anaspides alone among living Crustacea agrees with 

 them in this combination of characters, and there appears to be no 

 reason to doubt that it and Koonunga are really descendants of the 

 Syncarida of Carboniferous and Permian times. 



Bathynella natans, to which allusion has been made, is a minute 

 Crustacean (I/O mm. in length), described in 1882 by Vejdovsky 

 from two specimens found in a well in Prague. It has not since 

 been rediscovered. It appears to possess eight free thoracic somites. 

 There are no eyes. The antennules are uniramous, and the antennae 

 have a small exopodite. The first seven pairs of thoracic limbs are 

 biramous, and each has a single vesicular epipodite. The last pair 

 are vestigial. Only the first and last abdominal somites bear 

 appendages. If its structure has been correctly interpreted, Bathy- 

 nella would seem to be a degenerate member of the Syncarida, but 

 only the discovery of further specimens will enable its systematic 

 position to be definitely fixed. 



ORDER Anaspidacea, Caiman (1904). 



Family ANASPIDIDAE. Anaspides, G. M. Thomson. Family 

 KOOXUNGIDAE. Koonunga, Sayce. 



LITERATURE. 



1. Calnwn, IV. T. On the Genus Anaspides and its Affinities with certain Fossil 



Crustacea. Trans. Roy. Soc. Edinburgh, xxxviii. (4), pp. 787-802, 2 pis., 

 1896. 



2. On the Characters of the Crustacean Genus Bathynella, Vejdovsky. 



Journ. Linn. Soc. Zool. xxvii. pp. 338-344, pi. xx., 1899. 



