IMPERFECTLY-KNOWN SPECIES OP OSTBACODA. 441 



Genus Loxoconcha G. O. Sars. 



Loxoconcha punctata Thomson. (Plate XL VI. figs. 3-5.) 

 Loxoconcha punctata Thomson (i), p. 255, pi. xi. fig. B. 3a-k. 



Shell of the female, seen from the side (fig. 3), subrhomboidal, height equal to more 

 than two-thirds of the length ; extremities obliquely rounded, the anterior sloping 

 steeply above the middle and rounded off ventrally, posterior forming a bold curve 

 from below to the dorsum, where it ends in an abrupt angle; dorsal margin forming 

 a flattened arch with an excavation where it joins the posterior extremity, ventral very 

 slightly sinuated in the middle ; seen from above (fig. 14), lozenge-shaped, twice as long 

 as broad, widest in the middle, whence it tapers rather suddenly to the extremities, 

 which are subacuminate and nearly equal. Surface of the shell smooth, bearing 

 numerous small papillae ; valves flattened out at the extremities, forming a bordering 

 flange which is continued, though feebly, along the ventral margin. Colour generally 

 greyish, but variable, as is also the texture of the shell. Length "57 mm. The shell 

 of the male is rather larger ( - 7 mm.), and has the characteristic shape of that sex in 

 Loxoconcha. 



Hab. Otago Harbour, among seaweed and in rock-pools, Brighton, New Zealand. 



This species has been described and figured by Mr. G. M. Thomson (loc. cit.) ; but, 

 as the ' Transactions ' of the New Zealand Institute are not generally accessible, I here 

 re-figure the female. 



Genus Xestoleberis G. O. Sars. 

 Xestoleberis luxata, sp. n. (Plate XL VI. figs. 20-27.) 



Shell of the female compressed, subreniform, left valve much larger than the right, 

 and overlapping everywhere except on the ventral margin (figs. 20, 21) ; seen from the 

 side, nearly twice as long as high, highest behind the middle, depressed in front; 

 anterior extremity narrow, rounded but somewhat flattened, posterior wide and boldly 

 rounded ; dorsal margin forming a continuous curve, flattened toward the front, but 

 boldly rounded behind, ventral sinuated in front of the middle ; seen from above, 

 compressed, ovate, twice as long as broad, widest behind the middle, tapering gently 

 towards the front, well rounded behind ; shell-surface smooth, marked with numerous 

 very small circular papillae. Colour yellowish white. Length - 6 mm. Antennules 

 (fig. 24) six -jointed, bearing two setae on the second joint, one on the third, three on 

 the fourth, one on the fifth, and three on the sixth, all of them short ; the mandibular 

 branchia (fig. 26) consists of only two setae, and the animal is, in other respects, similar 

 to the typical Xestoleberis. 



Hab. On algae in Lyttelton Harbour, New Zealand. 



In most species of Xestoleberis there is some inequality of the valves, but in this 

 species it is more pronounced than in anv other known to me. 



