New (ji'ii a* of Terrestrial Isopoda. 21 



Generic Position. — The present species differs from the members 

 of the genus Phreatoicus, to which it is closely allied in two par- 

 ticulars, and to such an extent as to warrant the formation of a 

 new genus for its reception. These are the form of the uropods 

 and of the telson. In his generic description of Phreatoicus, Dr. 

 Chilton characterises the telson as " subcorneal,"* and each of 

 the species he describes has the telson terminated by a small, 

 prominent projection of very characteristic form. This process is 

 absent in our species and, though it is difficult by a single word 

 to express the form of the telson, yet it certainly is not " sub- 

 conical." Its sudden truncation and horse-shoe shape in trans- 

 verse section are features which mark it off strongly from the 

 form found in Phreatoicus. The uropods again are short and 

 stout and do not project appreciably behind the telson, differing 

 greatly in this respect from the long, styliform uropods of 

 Phreatoicus. 



A sexual difference found in the males of Phreatoicus again is 

 not found in the present species. As described by Dr. Chilton 

 the fourth pereiopod of the male is modified slightly so as to form 

 a grasping organ of the subchelate type ; whereas in our species 

 this modification does not occur and the appendage is similar to 

 the others. 



EXPLANATION OF PLATES III. and IV. 



Fig. 1. — Phreatoicopsis terricola. $ 

 Fig. 2.— Left Mandible. 

 Fig. 3.— Right Mandible. 

 Fig. 4. — Lower Lip. 

 Figs. 5, 5a. — First Maxilla. 

 Fig. 6. — Second Maxilla. 

 Fig. 7. — Maxillipede. 

 Fig. 8. — First Pleopod. 

 The magnification is indicated in the case of each figure. 



* Trans. New Zealand Institute, 1882, vol. xv., p. S9. Records of the Australian 

 Museum, vol. i., p. 151. Trans. Linn. Soc. London, vol. vi., pt. 2, p. 185. 



