860 PELECYPODA. [F ilibranchia . 



4. Philobrya modiolus, n. sp. Plate 51, fig. 16. 



Shel' small, equivalve, inequilateral, oblique, pyriform, almost 

 smooth, white Beaks close together, with a small fiat and oblique 

 prodissoeonch. Anterior end receding, straight, angled toward the 

 dorsal margin. Posterior end parallel to the anterior, almost straight, 

 with a blunt angle toward the straight dorsal margin ; basal margin 

 convex. Area keeled in front and behind the beaks. Sculpture con- 

 sisting of concentric growth-lines and very fine distant radial riblets, 

 which are mostly obsolete. Epidermis lost in all my specimens. 

 Colour white. Interior smooth, shining, white. Margins thin and 

 smooth, but strongly crenate at the upper posterior end. Hinge-plate 

 narrow, the anterior crenate area oval, with a rounded denticle in front, 

 the posterior crenellated area long and narrow. Ligament oblique, 

 rather large, internal. Adductor-xcar small, posterior. 



Diameter Ant. -post., 3 mm. ; dorso-ventral, 3 mm. : thickness 

 2 mm. : prodissoeonch, 0-2 mm. 



Type in my collection. 



Hab. Near the Bounty Islands, in 50 fathoms (type) ; Snares, 

 in 50 fathoms (Captain Bollons). 



I'ni/firks. The nearest ally of this species is P. meridionalis, E. A. 

 Smith (Dacrijdiu)n}, from Prince Edward and Marion Islands. 



Genus 2. HOCHSTETTERIA, Munier-Chalmas et Velain, 1876. 



Hochstetteria, Velain, C.R. Acad. Sc., 1876, (in part) ; Arch. Zool. Exp., vi, 

 1877. Type : H. crenella, Velain. 



Shell small, inequilateral, the anterior side shorter than the pos- 

 terior, but extending some distance in front of the beaks, regularly 

 rounded, mytiliform. Epidermis thin, without riblets or processes. 

 Shell perforated by minute tubules. Hinge-plate somewhat narrowed 

 between the 2 crenated areas. Ligament in a median fossette. There 

 are 2 adductor-scars. Prodissoeonch distinct or absent. 



The animal is most likely viviparous. 



Of this genus only five species have been recorded two from 

 the Islands of St. Paul and Amsterdam ; two from Port Alfred, Cape 

 Colony ; and one from New Zealand. 



1. Hochstetteria trapezina, Bernard, 1897. Plate 51, figs. 17, l~a. 



Hochstetteria trapezina, Bernard, J. de Conch., xlv, 1897, 18; 17, f. 3, 1, 

 pi. 1, f. 7 : Hedley, Rec. A.M., v, 1904, 89. Myrina minuta, E. A. Smith, 

 P. Mai. S., iii, 1898, 24 ; f. 4, p. 22. Adula minuta, Smith, Index, 94. 



Shell very small, transverse, much produced posteriorly, sub- 

 quadrangular. Beaks very close together, the prodissoeonch elongate 

 and considerably raised upon the definitive shell. Anterior end much 

 produced beyond the beaks ; posterior end truncated ; ventral margin 

 almost parallel to the dorsal. Sculpture consisting of numerous close 

 aud faint radial riblets, very often obsolete, and concentric growth- 



