272 DISCOVERY REPORTS 



In the majority of forms, as in the members of this family (Figs, i a, b), each maxillula 

 consists of two endites directed distally and corresponding to the endites of segments 

 I and 3 of the primitive axis ; the inner endite D is usually about two-thirds the length 

 of the outer one, and is in the form of a curved rod, which may enlarge towards its 

 distal end and bears one or two very short setae ; it springs from the centre of a basal 

 plate (i) which is the first segment of the primitive axis. At the outer side of the basal 

 plate is a smaller though broader plate (2), corresponding to the second segment of the 

 primitive axis, and from its outer distal extremity the second lobe of the maxillula arises, 

 consisting of the fused third segment and its endite (L^). This endite, which is stout and 

 slightly curved inwards, broadens distally and has its obliquely truncate extremity 

 armed with a double row of short stout spines. 



In all the species of Serolis except S. orbiculata, n.sp., and S. nototropis, n.sp., the 

 form of the maxilla agrees with that shown in Fig. i c. The three segments of the sympod 

 are again represented: the first is in the form of a plate (i) from near the outer margin 

 of which the second segment (2) arises ; this segment is in the form of a stout rod, the 

 upper third of which is expanded on its inner side to form a plate which appears to act 

 as a place of attachment for the muscles which hold its corresponding endite (L-) in 

 position. The latter is a broad lobe which tapers towards its proximal end where it 

 articulates with the upper half of the inner margin of its segment : its broad somewhat 

 rounded distal extremity usually bears about twenty pectinate setae. Arising from 

 a cup-like depression at the outer distal angle of the second segment of the sympod 

 is the third segment (3) of the primitive axis ; it lies in close proximity to the lower 

 part of the second endite {L") and at its inner distal oblique extremity articulates with 

 its corresponding endite. This lobe is cleft into two secondary lobes (L^ and L*), each 

 of which terminates distally in a truncate extremity which usually bears two strong setae 

 of the same type as those found on the second endite (L^). 



In the maxillae of S. orbiculata (Fig. i e) and S. nototropis (Fig. i d) the three seg- 

 ments of the primitive axis are again discernible, but the boundary of the second one is 

 difficult to follow. In some specimens of S. orbiculata the boundary of the plate-like 

 extension seemed to lie in the position indicated by the dotted line in the figure ; the 

 third segment (3), except for its proximal end, appears in S. orbiculata to be directly 

 continuous with the endite (L^) of the second segment as well as with its own endite (L^) ; 

 in S. nototropis the endite {D) of the third segment is separated by a suture. 



In both species the endite {U) is small and undivided (cf. condition in other species), 

 and that of S. orbiculata bears two and .S. nototropis four long, pectinate setae on its 

 truncate distal extremity. This type of maxilla may represent either a primitive or a 

 secondary condition; in support of the former is the fact that according to Caiman 

 (1909, p. 198) Hansen regards the two endites L^ and L* of segment 3 as having been 

 derived from the division of a single endite. In this case the condition seen in 

 S. orbiculata, where the endite (L^) is directly continuous with its segment, would be more 

 primitive than that in S. nototropis, where the endite (D) is cut oif from its segment, 

 and both would be more primitive than the type characteristic of the remaining species. 



