MARINE MOLLUSCA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 117 



left valve, especially, exhibit much elaboration of sculpture. When young, round, shining, 

 very fugitive scales exist, especially towards the ventral margin, whilst the interstices are 

 closely scobinate, there being four or five closely imbricate rows of minute squamae. The 

 right valve is by no means so elaborate, while the radiating ribs, irregularly placed, are 

 more than double in number, not, indeed, leaving much space for interstitial development. 

 Doubtless allied to P. limatula, Reeve,* and others of that section, the right valve, 

 indeed, is hardly separable in sculpture from that of limatula ; but its fellow is more 

 elaborately sculptured with close rows of interstitial scales than is the case in that 

 species, which is reported from Nightingale Island, Tristan d'Acunha (Rep. " Challenger " 

 Exped., xiii., p. 297, pi. xxi., figs. 5, 5a). 



Pecten sp. 



A right valve of Pecten sp., the auricles very detrite, covered with small Balani, 

 Membranipora, and other growths both without and within, but exhibiting about 35 

 variable, on the whole distinct, clearly cut, narrow longitudinal ribs, may be a form of 

 P. patagonicus, King. 



Hob. Port William, Falkland Islands. Trawled at 6 fathoms. 



Pecten pteriola, sp. n. (Plate, figs. 16, 16a). 



P. testa parva, insequivalvi, insequilaterali, albo-cinerea, obliquante, valva dextra minore, baud nitente, 

 concentrice rudi-striata, aliter laevi, auricula valvse hujus solum antica, lata, tenuisculpta, valva sinistra 

 convexa, arctissime liris concentricis incrementalibus lamellatis prsedita ; interstitiis fere' obtectis, innbone 

 dextrae acuto, incurve, margine dorsaliter utrimque eequali, recto, deinde apud marginem ventralem oblique 1 

 leniter rotundato. Pagina intus alba, mtida. 



Alt. 4, lat. 4'5, diam. 1'5 mm. 



Hob. Station 325. Dredged in Scotia Bay, South Orkneys, April 1903, at 9-1 0^ 

 fathoms. 



The nearest approach to this particularly interesting little Pecten, of which several 

 examples, all precisely similar, occurred, is P. aviculoides, Sm. (Rep. " Challenger" Exp. : 

 Lamellibr., xiii., p. 325, pi. xxii., figs. 5, 5o). It is, however, not only double the size 

 of that minute form, but also very differently sculptured, the ribs, so characteristic on 

 the left valve of the Challenger species, which came from Prince Edward Island, being 

 absent, and replaced by closely laminate concentric ridges or lirse. The specific name 

 is chosen from the likeness to species of Pteria, Scop. ( = Avicula, Lam.) in miniature. 



Amussium octodecim-liratum, sp. n. (Plate, figs. 17, I7a). 



A. testa compressa, albo-lactea, subpellucida, tenui, rotunda, fere aequilaterali, inaequivalvi, valvis diverse 

 sculptis, dextra pulcherrime' caricellata, striis multis erectis concentrice radiantibus, simul ac arctissimd longi- 

 tudinaliter striatula, interstitiis quadratulis, valva sinistra delicatd et arctissime concentric^ striata, auriculis 

 utrimque fere asqualibus, tenuisculptis, umbonibus ambobus acutis, subprominulis, pagina interna alba, nitida, 

 liris in valva utraque octodecim, ad margines extensis, preedita. 



Alt. 9, lat. 11, diam. 2'5 mm. 



Hob. Station 291, lat. 67 33' S., long. 36 35' W., trawl, 2500 fathoms. 



* Reeve, Conch. 'Icon., viii., pi. xxviii., fig. 124. 

 (ROT. soc. ED'IN. TRANS., VOL. XLVI., 147.) 



