CLASSIFICATION 269 



lateral portions of the tergum of the last thoracic somite, with its corresponding coxal 

 plates. 



(3) That group (iii), containing the remaining species, includes S. pogenstecheri, 

 Pfeffer, in which the tergum of the seventh thoracic somite is fused with that of the first 

 abdominal segment for a short distance on either side of the mid-dorsal line. Conse- 

 quently members of the "Australian group" do not bear characters which distinguish 

 them from all the remaining species. 



(4) That group (ii), containing the Australian species, is itself by no means a uniform 

 group and should be divided into three: 



[a) A group to contain those species in which the seventh thoracic somite is fused 

 with the first abdominal segment for a short distance on either side of the mid-dorsal 

 line. 



{b) A group to contain those species in which the seventh thoracic somite is not 

 only fused with the first abdominal segment but also with the tergum of the sixth 

 thoracic somite for a short distance on either side of the middle line. 



(c) A group to contain the species S. pallida, Beddard, and S. tuber ailata, Grube, 

 in which the middle portion of the seventh thoracic somite is absent, and the first 

 abdominal segment comes in contact with the tergum of the sixth thoracic somite. 

 The coxal plates of the seventh are well developed and fused with the small lateral 

 portions of the tergum of that somite. 



In group {a) would be included S. minuta, Beddard, S. bakeri, Chilton, S. pagen- 

 stecheri, Pfeffer, S.yongei, Hale, S. orbiciilata, n.sp., and S. nototropis, n.sp.; and in 

 group {b) S. australiensis, Beddard, S. elongata, Beddard, S. longicaudata, Beddard, 

 S. bouvieri, Richardson, S. platygaster, n.sp., and S. aspera, n.sp. 



(5) That members of group (ii) are not restricted to Australian waters, for the group 

 now includes, in addition to the Australian forms, S. pogenstecheri, Pfeffer, S. bouvieri, 

 Richardson, and the new species S. orbicidata, S. nototropis, S. platygaster and S. aspera. 



(6) That any new regrouping of the species would have to be based on the form of 

 the more posterior thoracic somites, and would result in the formation of five genera, 

 which would include the species represented in group (i), those in group (ii) subdivided 

 as shown above into {a), (b) and (c), and those in group (iii) excluding S . pagenstecheri 

 and S. bouvieri. 



(7) That S. beddardi and S. latifrons, in which the lateral parts of the tergum and 

 coxal plates of the last thoracic somite are present, and S. pallida and S. tuberctdata, in 

 which the central portion of the tergum of the seventh thoracic somite has disappeared, 

 represent the opposite ends of a series in which the remaining species are graded. 



After careful consideration, I have come to the conclusion that since the species 

 represent such a compact genus, it is undesirable to subdivide it by the formation of 

 four additional genera. 



Since writing the above, Nordenstam's paper (1933) has been published; in this the 

 author divides the genus Serolis into four sub-genera, namely, Spinoserolis, Serolis, 

 Homoserolis and Heteroserolis. 



