PARAMPHITHOIDAE 



i7i 



This genus contains a number of species which can be separated into two more or 

 less distinct groups, characterized by the tendency of the integumentary projections to 

 be on the one hand spiniform and on the other hand tuberculiform. Admittedly there 

 is no hard and fast division, but taking the Antarctic examples one would at first 

 sight be inclined to doubt whether macrodonta and robusta belonged to the same 

 genus. 



In the Antarctic fauna the macrodonta group causes no trouble. But in what may be 

 termed the inermis-robusta group we find a number of very closely allied forms which 

 illustrate in varying degrees the tendency among so many polar forms to develop 

 integumentary processes. 



Fig. 104. 2nd and 3rd joints of peraeopod 3 of Epimeria viewed obliquely from behind: a. inermis, Wlkr. 

 b. acanthurus, Schell. c. intermedia, Schell. d. puncticulata, Brnrd. e. excisipes, n.sp. (In d the faintly dotted 

 line indicates the bottom of the channel formed by the inner and outer keels.) 



These are mostly large forms and hence are amenable to a somewhat closer scrutiny 

 than many smaller forms. Thus in the study of the Discovery material I have become 

 aware of one feature which would seem to be of considerable value in diagnosing the 

 species. Unfortunately the three species in the Terra Nova collection were so clearly 

 differentiated on the more obvious features that the detail to which I am here drawing 

 attention did not obtrude itself. That, however, is of little consequence as two of those 

 species occur in the Discovery collection, and it is only robusta that I am not able to 

 include in the following comparison. 



The 2nd joints of peraeopods 3-5 have participated to a greater or lesser degree in the 

 general induration of the integument in these forms, for the purpose of closing the gap 

 between the 4th and 5th side-plates and the pleura of the pleon segments when the 

 animal is curled up. They thus become available for the development of rib-like 

 strengthening keels, marginal flanges and spiniform projections. 



