222 ON THE BEITISH SPECIES OF ENTOMOSTTfACA 



more abruptly behind to the short but broad terminal spine ; 

 ventral margin strongly convex, its" posterior portion usually 

 fringed with minute spines, which are continued round the 

 posterior extremity as far as the base of the terminal spine ; the 

 dorsal margin is much less strongly spinous; the two principal 

 abdominal processes united at their bases (fig. 2a). The spines 

 of the postabdomen twelve to fifteen in number and increasing 

 only slightly iu length from first to last ; the terminal unguis 

 has two serratures on its convex margin, while its concave 

 margin is finely ciliated and bears near its base a series of about 

 six principal curved spines (fig. 3), with another much more 

 minute row immediately in front of them. The pseudova are 

 often very numerous, varying from a few to as many as forty. 

 Shell marked throughout with more or less conspicuous quad- 

 rangular reticulations. Eye of moderate size, situated near the 

 front and toward the inferior margin of the head ; eye- spot about 

 half way between the eye and the posterior margin. Length,'''* 

 2-2J mm. The ephippial female has the ephippial portion of 

 the dorsal margin quite straight and a well-marked hump bounded 

 by distinct notches, intermediate between it and the head ; the 

 terminal spine in a line with the dorsum instead of being median 

 as in the pseudovial form. 



Male. — Yalves (fig. 4) narrower and more elongated than in 

 the female, tapering towards the posterior extremity, which 

 terminates in a moderately long median spine ; height equal to 

 half the length ; dorsal margin gently arched in front of the 

 middle, thence sloping in a nearly right line toward each ex- 

 tremity, ventral margin moderately arched, slightly sinuated near 

 the middle. Antennule (fig. 5) long, subcylindrical, truncated at 

 the apex, where it bears a few short sensory filaments and one 

 larger hooked seta, which is about half as long as the peduncle . 

 Postabdomen (fig. 7) wide at the base and tapered at the ex- 

 tremity ; pre-anal spines about nine, rather longer behind than 

 in front ; terminal unguis similar to that of the female. There 

 are two dorsal abdominal processes, one very short, the other 

 about twice as long as the terminal unguis, directed backwards 



* The measurements of length are in all cases exclusive of the spine. 



