278 Notices of Memoirs — A Triassic Isopod 



South "Wales, of a representative of the remarkable little sub-order, 

 the Phreatoicidea. To make clear the importance of this discovery 

 it is necessary to give a brief account of the existing members of the 

 group. 



The genus Phreatoicus was established thirty-five years ago, by 

 Professor Chilton, himself, for a blind species which he found 

 inhabiting subterranean waters in New Zealand. Other species, 

 some of them blind and some with functional eyes, were subsequently 

 discovered in streams and lakes of New Zealand, New South Wales, 

 Victoria, and Tasmania, and two species of terrestrial habitat were 

 also found. Three of the species were referred to as many genera 

 distinct from Phreatoicus and forming with it the family Phreatoicidse, 

 for which Mr. Stebbing in 1893 established the Tribe (now ranked 

 as a sub-order) Phreatoicidea. In 1914 Mr. K. H. Barnard greatly 

 extended the known range of the group by discovering a species of 

 Phreatoicus living in streams on Table Mountain at Cape Town. 



Fig. 1. — Phreatoicus australis, Chilton. Eecent. Mt. Kosciusko, New 

 South Wales. x 4. (After Qhilton.) 



The Phreatoicidea are distinguished from all other Isopods by 

 having the body more or less compressed from side to side, and 

 resembling in general appearance that of an Amphipod. This 

 resemblance, however, is no more than superficial, and the structure 

 of the animals shows that they are in no way closely related to .the 

 Amphipoda. 



As in nearly all Isopods, seven somites are distinct in the thoracic 

 region, and the telson is not separated from the last abdominal 

 somite. In the Phreatoicidea, however, the first five abdominal 

 somites are not only distinct and movable but they are of con- 

 siderable size. This is of some importance as a primitive character, 

 since the abbreviation of the abdominal region is one of the most 

 characteristic features distinguishing the Isopoda from the other 

 orders of Malacostraca. Even when, as in many Flabellifera, the 

 abdominal somites are distinct from one another, they are crowded 

 together, and the greater part of the length of the abdomen is 

 formed by the enlarged terminal segment. The great development 

 of the side-plates (pleura) of these abdominal somites in the 

 Phreatoicidea, and the fact that they are directed downwards 

 instead of laterally, are characters of less morphological significance, 

 but they contribute to the Amphipod-like aspect. Another character 



