56 THE VOYAGE OF 11. M.S. CHALLENGER. 



t 

 is a single strongish tootli in the right valve just Lenoath the uml>o, with a large deep 

 triangular excavation behind it, the hinge-plate being rather deeply grooved on the anterior 

 side. Immediately under the dorsal margin, a little behind the beak and above the 

 triangular excavation mentioned above, there is a small shallow elongate pit, no doubt 

 for the reception of a small internal ligament. The muscular impressions are indistinct. 



Length 7 nnn., height b\, presumed diameter of a perfect specimen 4. 



Habitat. — Station 185b, east of Cape York, North Australia, in 155 fathoms; coral 

 sand. 



Although not minutely granulated like the typical forms of Poromija, still, in the 

 composition of the hinge, this species, so far as one can judge from right valves only, 

 accords with that genus. The interior has a similar semipearly character, and is 

 radiately substriated, so that the location is probablj' correct. 



Subfamily Myin^. 



Mya, Linne. 

 Mj/a sp. 



Habitat. — Flinders Passage, Torres Strait, in 7 fathoms. 



Only a minute left valve of a species of Mya was obtained at this locality. It is 

 not unlike Mya japonica in outline, and possibly it may be the young of that form. 

 As no species of the genus has been recorded from this district, its occurrence may be 

 worthy of mention. 



Family M a c t r i d .e. 



Subfamily Lutrariin.e. 



Pacta, Gray. 



«> Raeta pulcheUa, (Adams and Reeve). 



Poromi/a piildiella, Adams and Reeve, Zool. Voy. Samarang, p. 83, pi. xxiii. fig. 1. 

 Raeta 2Julchel.la, H. and A. Adams, Gen. Moll., vol. ii. p. 386. 

 Madra ronfralis, De.shayes, Proc. Zool. Soc. Lond., 1854, p. 69. 

 Mudra rostralU, Reeve, Con. Icon., vol. viii. pi. xxi. fig. 119. 



Habitat. — Off Yokohama, in 8 to 14 fathoms ; and Station 233c, off Japan, in 

 12 fathoms. 



This species was originally described from specimens dredged off the shores of 

 Borneo, and again as Mactra rostralis, from Japanese examples. It is more elongate 

 than the young of the American Pacta canaliculata, and somewhat more equilateral. 



