304 THE VOYAGE OF H.M.S. CHALLENGEK. 



With this exceptiou, and a very slight variation iu the microscopic sculpture, there 

 do uot at present appear to be any further or sufficient grounds for specifically separating 

 the Philippine examples. If we had a more extended series of specimens for examination, 

 it is possible further difi"erences would present themselves. 



Pecten suhhyalinus, n. sp. (PI. XXII. figs. 2- 2a). 



Testa compressa, tenuissima, vitrea, nitida, aliquanto intequivalvis ; valva sinistra 

 paulo convexior, fere la^vis, striis paucis concentricis aliisque radiantibus sculpta ; valva 

 dextra striis concentricis regularibus ornata. Auriculse infequales, bene definitaa, anticis 

 paulo majoribus, ilia valvas dextraj radiatim lirata, mediocriter profunde sinuata. Margo 

 valvse infra sinum rectilinearis, haud denticulatus. 



Length 7 mm., height Ih, diameter 2. 



Habitat. — Station 310, off the w'est coast of Southern Patagonia, in 400 fathoms. 



This species belongs to the same group as Pecten vitreus (Chemnitz), from which it 

 differs both in sculpture and form. In that species the posterior auricles are scarcely 

 defined, whilst in the present form there is a well marked umbonal rectilinear ridge, 

 from the apex to the side margin. The anterior umbonal slope in that species is incurved 

 and toothed, in this it is straight and edentulous. 



Pecten distinctus, n. sp. (PL XXII. figs. 3-3a). 



Testa parva, compressa, paulo ina3quivalvis, tenuis, subpellucida, haud nitida, sordide 

 albida. Valva dextra parum convexa, concentrice tenuissime lamellato-striata, sinistra 

 paulo convexior, liris concentricis fortioribus instructa, liris radiantibus paucis indistinctis 

 ornata. Auriculae insequales, definitse, anticis majoribus, ilia valvse dextrce radiatim 

 lirata, inferne haud profunde sinuata. 



This little species is slightly inequivalve, the left valve being rather deeper than the 

 other. It is compressed, thin, a little transparent, not glossy, of a dirty white colour, 

 and has difi"erently sculptured valves. The right has much finer concentric lirse than the 

 left, and has no radiating lines, which, however, are not particularly conspicuous in 

 .the other valve. The umbones are rather acute, the straight or feebl)^ incurved sides 

 forming an apical angle of about 105°. The ears are unec[ual, the front ones being the 

 larger. That in the right valve is ornamented with six or seven fine lirse, which cover 

 the greater part of the surface, leaving only a narrow plain groove at the moderately 

 deep sinus. 



Length 8 mm., height 7\, diameter 2. 



Habitat. — Off Marion Island, in 100 fathoms. 



In this species the ears are depressed and well marked off from the rest of the surface. 



