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



mediana lata sculpta. Umbones centrales, ad apicem la3vigatum hand acuti, supra 

 marginem dorsalem vix producti. Pagina interna nitida, sculpturam externum exhibens. 



Length 2 mm., height 3^, diameter 1^. 



Habitat. — Station 23, off Sombrero Island, West Indies, in 450 fathoms ; Station 24, 

 off Culebra Island, in 390 fathoms. 



This interesting little species is readily recognisable by the almost total absence of 

 radiating sculpture, and the very slender concentric lamellae. The radiating lirse which do 

 exist are very faint, and occur only down the central portion of the valves, giving the laminae 

 a somewhat frilled appearance. The auricles are equal and scarcely defined, the lateral 

 margins of the valves being regular and faintly curved at the upper part, and not constricted. 



Lima sarsii is more distinctly radiately ribbed, is said to have the hinge-plate 

 "bluntly but distinctly crenulated across," and the front m;u'gin "strongly crenate and 

 notched within," features not occurring in the present species. 



Family P E c T I N i D .E. 

 Pecten, Midler. 

 Pecten asperrimus, Lamarck. 



Pecten aspernnms, Lamarck, Anim. sans vert., ed. 2, vol. vii. p. 14-5. 



Pecten a-'^perriimis. Reeve, Conch. Icon., vol. viii. pi. xx. fig. 75. 



Pecten asperrimus, Sowerby, Tlies. Conch., vol. i. p. 75, pL' xvii. fig. 156 (157 and l">iS?). 



Juv. =Pec<e?j australis, Sowerby {non Pliilippi), op. eit., p. 76, pi. xix. figs. 219, 220. 



Pecten australis, Reeve, loc. cit., pi. xxv. figs. 103, a, Ij. 



Habitat. — Station 162, off East Moncoeur Island, Bass Strait, in 38 fathoms. 



In the young state the rays of this species consist of a central ridge and two finer 

 lirae, one on each side, all very finely squamate as in Pecten australis. At maturit}' the 

 lirse usually number three on each side. Tlie closely allied Pecten prxtniim, Eecve, has 

 a broader central ridge to the rays, which in consequence look rounder, and the auricles 

 are larger. Like many other Pectens, this is also variable in colour, in some instances 

 being of a plum colour, in others orange or scarlet. The Challenger specimens are 

 uniformly reddish-orange. 



Pecten patagonicus, King. 



Pecten patagovicus. King, Zuol. .Joiun., vol. v. p. 337. 



Pecten patagonicus, Sowerby, Thes. Conch., vol. i. p. 54, pi. xiii. fig. 16. 



Pecten patagonicus. Reeve, Conch. Icon., vol. viii. pi. xxvi. fig. 110. 



Pecten patagonicus, Smith, Proc. Zool. Soc. Lond., 1881, p. 44. 



J\iv. = Pecten nifiradiafus. Reeve, op. cit., pi. xxxii. fig. 147. 



1 = Pecten australis, Philippi, Wiegmann's Archiv f. Naturgesch., 1845, p. 56. 



Habitat. — Station 312, South Patagonia, in 9 fathoms; and Station 315, Falk- 

 land Islands, in 12 fathoms. 



