REPORT ON THE LAMELLIBRANCHIATA. 29 



Of this small species only a single specimen was dredged. The lower portion of the 

 tube is somewhat ovate, and broader at the inferior end. Above it is rather suddenly- 

 contracted into a small, i)lain tube, which is partly partitioned off within, from the main 

 cavity, leaving only a narrow elongate opening of communication. The base and sides of 

 the swollen portion of the tube are ornamented with numerous short tubuli. The interior 

 of the tube is strengthened on the side of the free valve by a slender central ridge 

 passing from the umbo of the fixed valve up the opposite side. The free valve is longer 

 than high, considerably inequilateral, thin, white, very compressed, broadly rounded 

 anteriorly, narrowed and produced behind. It is marked with rather coarse lines of 

 growth, and ornamented at the upper part with very fine granular lines which radiate 

 from the umbo not quite half-way across the valve. The beak is small, acute, slightly 

 raised above the hinge line, and situated considerably in advance of the centre. The 

 interior is glossy, somewhat wrinkled concentrically, and faintly substriated in the 

 opposite direction. The muscular scars and pallial sinus are very indistinct. Just 

 behind the apex of the umbo, and within the dorsal edge, there is a minute narrow 

 groove terminated behind by a small denticle which receives a minute ligament. 



Length of free valve 12 mm., height 8; greatest width of tube 9, smallest width 4; 

 length of opening of communication between the narrow and swollen portions of the 

 tube 3, width 1. 



Habitat. — Torres Strait, in 3 to 11 fathoms. 



Family Myidje. 



Subfamily Corbulin.e. 



Corbitla, Bruguiere. 



Corhida tunicata, Hinds. 



Corhula tunicata, Hinds, Proc. Zool Soc. Lond., 1843, p. 55. 



Corhula tunicata, Reeve, Conch. Icon., vol. ii. fig. 5. 



Corhula tunicata, Tryon, Amer. Journ. Concli., vol iv. Appendix, p. 66. 



Habitat. — -Port Jackson, Sydney, in 4 to 18 fathoms; off Amboina, in 15 to 25 

 fathoms; and Station 189, Arafura Sea, in 25 fathoms; green mud. 



The specimens from the first two Stations are fine large shells agreeing in every 

 particular. The largest example is 28 mm. long, 19^ high, and 16 in diameter. Two 

 specimens from the Arafura Sea are somewhat abnormal both in form and sculpture, 

 occupying an intermediate position between this species and Corbida crai^m. The latter 

 species is more equivalve than Corbida tunicata, has the left valve sculptured throughout 

 like the right, which has a much smaller and less curved-over umbo than that of the 



