74 THE VOYAGE OF H.M.S. CHALLENGER. 



the dorsal margin above ; dorsal margin boldly arched, forming in front a continuous 

 curve with the anterior margin, slightly sinuated behind, and joining the posterior 

 extremity at an acute angle ; ventral margin deeply sinuated in the middle, and curving 

 upwards with a bold sweep behind ; seen from above, the outline is boat-shaped, obtusely 

 pointed in front, broad and truncated behind ; the sides sinuous, curved, and falling 

 slightly inwards at an obtuse angle near the posterior extremity ; width and height 

 nearly equal ; end view broadly ovate, widest above, the sides converging towards the 

 ventral margin, which is narrow and keel-shaped. The central portion of each valve is 

 excavated so as to form a large subrotund pit, above which, towards the dorsal margin, is 

 a series of four or five similar, but not quite so large, excavations ; these are separated 

 from each other by rounded ridges, and round about this group of large fossse are 

 disposed several much smaller hollows ; the dorsal surface is very broad, has a deep 

 longitudinal furrow along the greater part of the hinge-line, and shows conspicuously 

 the transverse ribbing which separates the lateral fossae. Length, 1-5 8th of an inch 

 (•43 mm.). 



The specimens described by me in the Zoological Transactions were from Hobson's 

 Bay, Australia ; but those figured by Reuss and Egger were fossils from the European 

 Tertiary formations. The Challenger specimens are from ofi" East Moncoeur Island, Bass 

 Strait, 38 to 40 fathoms (Station 162) ; and from Port Jackson, Australia, 2 to 10 

 fathoms. 



[PL XIV. fig. 7, a-d. a Shell seen from left side, h from above, c from below, 

 d from front. Magnified 60 diameters.] 



22. Cythere reussi, G. S. Brady (PL XIV. fig. 2, a-d). 



Gythere reussi, Brady, Les Fonds de la Mer, torn. i. p. 153, pi. xviii. figs. 9, 10. 



Shell, seen from the side, oblong, subquadrate ; greatest height situated near the 

 anterior extremity, and equal to half the length ; anterior extremity broad, obliquely 

 rounded, posterior narrower, rounded ofi' above, somewhat angular below, and having 

 below the middle one or two short stout teeth ; dorsal margin nearly straight, sloping 

 gently from before backwards, ventral slightly sinuated in the middle ; seen from above, 

 the outline is compressed, ovate, more than twice as long as broad, and having the 

 greatest width near the middle ; lateral margins gently curved ; extremities bimucronate ; 

 the anterior wide and truncated ; the posterior narrower, and deeply notched between 

 the two terminal teeth ; end view broadly ovate, almost circular, keeled on the ventral 

 margin. The valves are throughout sculptured with numerous closely-set, irregularly- 

 shaped fossae of small size ; the tubercles over the anterior hinge-joint are conspicuous, 

 and the junction of the valves on the dorsal surface is marked by a deep longitudinal 

 groove. Length, 1-5 0th of an inch ("5 mm.). 



