AUSTRALIAN MALACOSTEACA. 277 



Thoracic segments increasing slightly in breadth posteriorly. 

 Epimera of first segment not distinct ; those o second, third and 

 fourth small ; the rest larger ; those of the sixth and seventh 

 segments produced to an angle posteriorly. Greatest breadth of 

 the abdomen more than half the length ; in old specimens there 

 is a low rounded mesial dorsal ridge ; the extremity narrowing 

 suddenly and rounded in old specimens but sub-acute in younger. 

 Internal antenna? very short, scarcely reaching the extremity of 

 the third joint of the peduncle of the outer pair; basal segment 

 of the peduncle short and thick, quadrate ; second segment 

 shorter and much narrower than the first ; third as long as the 

 first, slender, cylindrical. External antenna? nearly equal in 

 length to the head and first six segments of the thorax ; three 

 basal joints short and stout, fourth the longest ; flagellum longer 

 than the peduncle, tapering, composed of about twenty articuli. 

 Colour very inconstant, sometimes olive-green, sometimes rich 

 brown, variously marked with bands of dull yellow. Length of 

 largest specimen If in. 



Griffiths' Point ; Port Philip ; Tasmania. 



The nearest described ally of this species appears to be I. slrieta 

 of Dana, from which it is distinguished, among other points, by 

 the much greater number of joints in the outer antenna?. 



480. Idotea excavata. A.M. 



Idotea excavata, Haswell, 1. c., p. 2. 



Length of body about four and a half times the greatest 

 breadth. Head very small, much narrower than the thorax. 

 Epimera of the last six thoracic segments distinct, increasing 

 in size posteriorly the last three acutety angulated behind. 

 Abdomen about twice as long as broad, scarcely equal in length 

 to the last four segments of the thorax, terminated posteriorly by 

 a concave border bounded on either side by an acute tooth. 

 Internal antenna? short, a little longer than the three basal 

 segments of the peduncle of the outer pair ; flagellum shorter 

 than the last segment of the peduncle. Outer antenna? about 

 two-thirds of the length of the body ; the peduncle slightly 

 compressed dorso-ventrally, the two last joints nearly equal in 



