856 PELEOYPODA. [Filibranchia. 



culate, except at the basal byssiferous foramen and the upper part 

 of the posterior margin. Hinge-plate narrow, arcuate, smooth behind 

 the beak, with 5 to 6 short and straight anterior teeth, and 5 to 6 

 oblique, sometimes slightly hooked, posterior teeth. Ligament very 

 small. Adductor-scars unequal, the anterior smaller. Pallial line 

 simple. 



Length, 3-5 mm. : height. 2-8 mm. ; diameter, '2-6 mm. 



Type in my collection. 



Hob. Bounty Islands, in 50 fathoms (Captain Bollons). 



Remark. This species is smaller, much more inflated, more dis- 

 tinctly radially striated, and with the beaks much more anterior than 

 A. aucklandica. 



Fam. PHILOBRYID^I, Bernard. 



Animal like that of Limnpsis, usually without an anterior adductor 

 muscle. Carnivorous. 



Shell small, equi valve, very inequilateral ; anterior end very little 

 developed, or atrophied. Byssus short and thin, passing through a 

 narrow opening between the anterior margins of the valves. Um- 

 bones projecting and formed by the embryonic shell or " prodisso- 

 conch,'' straight or slightly curved toward the anterior end (proso- 

 gyrate). Umbonal cavity well marked. Ligament internal, or only 

 partly external, median or directed backwards ; area linear, epider- 

 mical or absent. Hinge with strong vertical crenellations; in front 

 and behind this double border of crenellations there are marginal 

 teeth or ridges, which sometimes become obsolete. Test not nacreous, 

 without a prismatic layer, sometimes polished, finely tubular. 



Secondary to Recent. 



KEY TO GENERA. 



A. Beaks always with a prodissoconch ; anterior end but little 



developed and advancing ; only 1 adductor-scar . . PHILOBRYA. 



B. Beaks with or without prodissoconch ; anterior side extend- 



ing a short distance in front of the beaks ; shell minutely 



perforated ; 2 adductor-scars . . . . . . HOCH.STETTERIA. 



Genus 1. PHILOBRYA. P. Carpenter, 1872. 



Philolrn/a, P. Cpr., Smiths. Misc. Coll., x, 1872 ; Bernard, J. de Conch., xlv. 

 18!'7, 9. Type : Brt/opliila sr-tosfi. Cpr. Bryophila, P. Carpenter, 1864 ; 

 preoccupied. Hochstetteria, Velain et Munier-Chalmas, 1876 (in part). 

 Li'mami, Tate, 1886. 



Shell very inequilateral, anterior side very little developed and but 

 little advancing in front of the embryonic shell. Form subquad- 

 rangular, elongated in the dorso-ventral direction. Anterior end very 

 short, .-ibruptly truncated ; posterior end continuing the hinge-plate ; 

 ventral margin rounded. Epidermis thick, extending beyond the 

 margins of the valves, and forming hairy riblets, to which may corres- 

 pond riblets of the shell. There is only 1 adductor-scar in each valve. 

 Beaks close together, surmounted by the prodissoconch, which forms 



