REPORT OiV THE LAMELLIBRANCHIATA. 305 



Pecten clathratus, Martens (PI. XXII. figs. 4-4o). 



Pedeii clathratus, Martens, Sitzungsb. d. Gesellsch. natuif, Freundi-, IJerlin, 1881, p. 79. 



Testa tenuis, subpfUucida, iutequivalvi.y ; \alva de.xtra planiuscula, parum nitida, 

 incrementi lineis striata, striisque microscopicis radiantibus, inidique suljcancellata ; valva 

 sinistra profundior, lanicllis coucentricis, tenuibus, lirisquc iiimicrosis radianti1)us fili- 

 formibus cancellata. Auriculae fere jequales, antica valvse dextr?e lamellis incrementi 

 sculpta, ad extremitatem rotundata, inferue profunde siiiuata. 



This species is considerably inequivalve, thin, rather pellucid and compressed. The 

 right valve is only a little convex, and, as it were, fits within the other valve, although in 

 reality its outer margin, which is upturned, does extend to the edge of the left valve. It 

 is a little glossy, sculptured 'svith very fine lines of growth, and has a microscopic, 

 subgranular, radiating structure. The left valve is much deeper and ornamented with 

 stronger sculpture, consisting of very fine concentric lamellae and still finer and more 

 numerous radiating ones, together producing a pretty cancellated appearance. The ears 

 are not very unequal, tlie anterior being only a little larger than the posterior. The 

 front one in the right valve is broadly curved at the end, rather deeply cut in under- 

 neath, and sculptured with strongish lines of growth. The umboucs are acute, the sides 

 forming an apical angle of about 100 degrees. 



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



Habitat. — Oft' Christmas Harbour, Kerguelen Island, in 120 fathoms. 



The shells obtained at this locality apparently belong to tlie Pecten clathratus of 

 von Martens, Ijut as 1 am not absolutely certain I have deemed it advisable to give the 

 above description. 



Pecten aviculoides, n. sp. (PL XXII. figs. 5-5«). 



Testa parva, vakle inajquivalvis, paulo obliqua, tenuis, sordide albida. Valva dextra 

 planiuscula, nitida, striis incrementi tenuissimis sculpta, sculptura microscopica sub- 

 reticulata ornata. Valva sinistra profunda, lamellis coucentricis, validis, costisque ad octo 

 radiantibus fortiter cancellata. Aniiculne subfequales, auricula valvar dextrae antica 

 lamellis incrementi liriscjue paucis radiantibus instructa, inferne subprofunde sinuata. 

 Linea cardinis longa, longitudinem totam testa) a;quans. Umboncs centrales, ille valvag 

 sinistra^ paulo supra marginem productus. 



This species is remarkable for the great difference in the sculpture of the valves. It 

 is rather like a minute Avicula in form, slightly oblique in growth, very inequivalve, 

 thin, and of a dirty white colour. The right valve is very slightly convex at the centre, 



(ZOOL. CHALL. EXP. — PART XXXV. — 1885.) Mm 39 



