of the North Atlantic and of North-Western Europe. 699 



Genus 5. Conchoecissa, Claus. 



Rostral process beak-like, long, sharp and strongly curved ; sinus moderately 

 large ; hinder extremity of each valve produced dorsally into a backward-pointing 

 sharp spine, and ventrally into a rounded or obtusely-pointed spine. Shell 

 distinctly striated, and towards the free margins strongly reticulated; ventral 

 margin more or less roughened with minute projecting spines; mandible with 

 well-developed tooth- ridges and four large lancet-shaped spines. 



1. CoNCHCECissA, armata, Claus. 

 (PI. LXIV., figs. 1—5.) 



1890. Conchoecissa armata, . . Claus, '' Die Gattungen und Arten der mediter- 



ranen und atlantischen Halocypriden," p. 19 



1891. ,, ,, . . Claus, "Die Halocypriden des atlantischen 



Oceans und Mittelmeeres," p. 70, pis. xvi., 

 xvii., xviii. 



Shell elongated, lower in front than behind, greatest height equal to less than 

 half the length ; seen from the side the outline is sub-quadrate, rectangularly 

 truncate behind, ventral margin rather protuberant ; striation of the shell well 

 marked, the ventral and anterior portions strongly reticulated with transverse 

 rows of elongated sub-quadrate areas, which towards the postero-dorsal angle 

 become nearly square, and in the central area almost give place to the longitudinal 

 strise. Rostrate process large, very acute at the apex, at first directed straight 

 forwards, afterwards slightly curved downwards ; lower margin of the antennal 

 sinus well arched forwards, leaving a slight hollow at its junction with the base of 

 the rostrum. Infero-posteal corner produced into a conspicuous acute spine- 

 shaped process, that of the right valve being longer than that of the left ; infero- 

 posteal corner also produced into a blunt, spine-shaped process, which, however, 

 is not so large as the dorsal spine. The lower border of this process is repre- 

 sented by Claus as serrated, but it is not so in our specimen. The chief 

 peculiarity of this structure is that it is not a production of the edge of 

 the valve, but takes its origin at some distance within the border (PI. LXiv., 

 fig. 1). Frontal tentacle of the female (fig. 3), much longer than the antennule, 

 capitulum slender, only slightly club-shaped, and having a few small marginal 

 spinules; in the male the organ is much shorter, the capitulum distinctly clubbed, 

 and bent at a right angle to the peduncle. The principal seta of the antennule of 

 the male bears eight or nine pairs of unusually strong booklets. The setae and 



