40 



legs is situated at or behind the middle of the trunk, and if seen from below, near or on 

 the lateral margin; as a rule it is shorter than the first pair, the peduncle is not much 

 thicker than the rather short inner branch, whereas the outer branch — if there is one — 

 is triangular and often ends in a short seta. The terminal setae of the inner branch vary 

 as much in length as those of the outer branches of the first pair of legs, and one of them 

 can attain to half the length of the animal. The caudal stylets are usually situated rather 

 close to each other, most frequently near the posterior end of the body, sometimes very much 

 to the front about at the middle of the trunk, especially where it is very large, as in Sphmr. 

 Bonnieri and in S. frontalis (pi. VII) ; in the latter species they even appear in front of the 

 second pair of legs. Both stylets as a rule are rather short, sometimes very short, nearly 

 cylindrical; one terminal seta on each stylet is often rather or very long, occasionally excee- 

 ding in length the above-mentioned long setae on the trunk-legs. — Several species of 

 Sphatronella deviate now in one, now in more respects, from this description which is based 

 on the main bulk of the species. In Sphcer. modesta (pi. IX, fig. 2 f and fig. 2 h) the first, 

 and especially the second pair of legs are considerably reduced in size etc., whereas the 

 caudal st3 r lets are comparatively large and constructed like those of the female (see above). 

 In S. decorata (pi. VIII, fig. 3 f and fig. 3 g) the two pairs of trunk-legs are very much 

 alike, each leg consisting of a short basal part with two short branches, and each branch 

 ending in a thick, but rather short seta; caudal stylets are wanting. Concerning S.microce- 

 phala (pi. VIII, fig. 2g and 2h) which deviates considerably and is difficult to understand, 

 I refer to my description in the systematic part of this work. In S. curtipes (pi. X, fig. 2 f 

 and fig. 2 g) both pairs of legs are very small, slender and 2-jointed, the caudal stylets are 

 quite minute and situated far from each other on the posterior margin of a long and broad, 

 but not much projecting eminence, the posterior angles of which are decorated with peculiar 

 rounded processes and knots (might the whole formation possibly be a reduced abdomen?). 

 It has been mentioned already that trunk-legs and caudal stylets have disappeared altogether 

 in several species of SphceroneUa as well as in Mysidion and Aspidoecia. 



In the species belonging to Stenothocheres and Aspidoecia the body of the male is 

 quite naked, whereas all the other species are more or less clothed with hairs. In not 

 a few species the frontal margin is furnished with very short hairs or with fine spiniform 

 processes (the species of Sphesronella which live as parasites on Cumacea). In nearly all 

 species the margin of the lateral borders of the head are trimmed with a series or a stripe 

 of hairs usually of medium length, which as a rule extends towards the front in a curve 

 round the base of the antennulse, ending just in front of it ; posteriorly it follows the lateral 

 margin up to its curved extremity, whence (or a little in front of it) the stripe continues 

 across the sides and the back, now straight on, now curving or in a broken line, now advan- 

 cing, now receding obliquely. This line I consider as forming the boundary between the 

 head and the trunk, its hairs being now very long (pi. Ill, fig. 3 i ; pi. VI, fig. 1 d), now of 

 the same length as those which cover the sides of the trunk. Sometimes (e. g. pi. IV, fig. 3 h) 



