IMPEEPECTLY-KNOWN SPECIES OF OSTBACODA. 443 



ventral deeply sinuuted in front of the middle, behind which it is slightly convex ; 

 seen from above, the outline is narrowly ovate, nearly thrice as long as broad 

 (fig. 9), rounded behind and tapered gradually to the obtusely-pointed anterior 

 extremity. Shell-surface covered with closely-set angular pittings, except on the 

 marginal flange (fig. 10), the flange itself marked with closely-set, fine, radiating 

 lines (lacunse'?) on its broad inner zone, and on the narrower outer zone with 

 distant short hairs. Length '66 mm. Antennules (fig. 11) six-jointed, each of the 

 last four joints bearing a stout apical spine, the last three having also one or two 

 setse which are not very much longer than the spines ; urticating seta of the antenna 

 slightly longer thaTi the limb ; poison-gland large and lobose. Mandible (fig. 12) stout, 

 broad, and many-toothed ; palp three-jointed, the long middle joint being again imper- 

 fectly divided into three, terminal joint much narrower than the rest, finger-like, and 

 bearing three broad apical setae and two short hairs ; the long median joint has an 

 apical brush of seven long hairs arising from a short external process ; its inner 

 margin has three very stout, curved, plumose setse, that of the distal segment being 

 much longer than the other two; the middle of the 'outer margin has a fascicle of 

 very short, fine hairs ; the short basal joint bears two very small, plumose branchial (l) 

 setse. Three pairs of feet, sparingly setiferous (figs. 13, 14), with strong curved ungues. 

 Copulative organs complex (fig. 15), enclosing a coiled spermatic duct, with two stout 

 plumose setse on the free margin. Female unknown. 



JIab. A few specimens taken in Lytteltou Harbour among algse. 



The antennae of this species with their long and stout urticaiing setae, and the 

 mandible-palps with their slender terminal joint and stout, falcate setse, correspond 

 closely with the same organs as seen in Cythere alhomaculata Baird, and in no other 

 species with which I am acquainted. 



Ctthere innominata, nom. nov. (Plate XLVI. figs. 1, 2.) 

 Cythere truncata^ Thomson (i), p. 254, pi. xi. fig. C. ia-c. 



Shell, seen laterally (fig. 1), subquadrate, highest in front, greatest height much more 

 than half the length ; anterior extremity broadly rounded, irregularly crenulated or 

 almost dentated ; posterior narrow, rounded off above and below, subtruncate below 

 the middle, but deeply excavated above ; dorsal margin sloping gently and in a slightly 

 sinuous line from the front ; ventral nearly straight behind its junction with the anterior 

 encircling fillet, gently upcurved toward the posterior extremity ; seen from above 

 (fig. 2), elongated, compressed, widest behind, nearly thrice as long as broad, lateral 

 margins converging gradually, but with irregular sinuations from near the hinder end 

 to the front, whicli is obtusely pointed ; from the widest point the sides converge 



' This specific name has been already used by Reuss for a Tertiary species. I therefore propose the new 

 name innominata. 



