170 THE VOYAGE OF H.M.S. CHALLENGER, 



more quadrate, and has fewer radiating lines. As but a single left valve was obtained 

 I am unable to complete the description of the hinge ; however, the right valve would 

 probably have a single tubercular tooth. 



Verticordia tornata (Jeffreys) (PI. XXV. figs. 9-96). 



Pecchiolia tormita, Jeffreys, Ann. and Mag. Nat. Hist., 1876, vol. xviii. p. 494. 



Habitat. — Station 70, west of the Azores, in 1675 fathoms; also Station 106, Mid 

 Atlantic, between Sierra Leone and Brazil, in 1850 fathoms. 



Of this species only some fragments were described by Jeffreys. Two perfect valves 

 from Station 70, and a complete specimen from Station 106, were obtained by the 

 Challenger, and enable me to supplement the description in the Annals. 



This species is globose, somewhat Isocardia-Vike, nearly equilateral, but a very little 

 inequivalve, the right valve very slightly overlapping the left along the ventral margin 

 and the hinder dorsal slope. The minute tubercles are arranged in more or less regular 

 radiating series, their irregularity being especially noticeable at the hinder end. The 

 umbones are well produced, involuted and directed towards the front, and the ligament 

 is external and placed in a small sunken groove upon the hinge-line behind the 

 conspicuous prominent tooth in the right valve, and posterior to the thickened termina- 

 tion of the front dorsal margin in the left. 



Length 13 mm., height 1.3, diameter 10. 



The somewhat different position of the ligament in this species is, I think, hardly of 

 generic importance, as the form and granular surface so closely approach Verticordia 

 ivoodii and Verticordia quadrata, which connect it with typical species such as Verti- 

 cordia ornata and Verticordia australiensis. 



Family T R i D a c N i d .^. 



Tridacna, Bruguiere. 



Tridacna crocca, Lamarck. 



Tndacna crocea, Lamarck, Anim. sans vert., ed. 2, vol. vii. p. 10. 



Habitat.— Station 186, off Cape York, North Australia, at a depth of 8 fathoms; 

 coral mud. 



The single specimen from the above locality agrees very fairiy with the figure in the 

 " Conchylien-Cabinet " of Chemnitz referred to by Lamarck. The species of this genus are 

 extremely puzzling, and I believe that the young of the largest known shell {Tridacna 



