REPORT ON THE LAMELLIBRANUUIATA. 73 



Lyonsiella, M. Sars. 

 Lyonsiella jeffreysii, n. s^]i. (I'l. XXV. figs. 1-1/^). 



Testa tenuis, globosa, inajquilatenilis, aiitice rcctc truucata, postice et iiifonic arcuata, 

 sordide albida, intus margaritacea, undique minute granulata, lineis gracillimis numerosis 

 radiantibus instructa, striisque incrementi hie illic sublamellatis oruata. Margo dorsi 

 anticus brevis, rectus, horizontalis, posticus longior, declivis, vix excurvatus. Lunula 

 concava, tota in valva dextra. Umbones incurvati, antrorsum versi. Cardo edentulus. 

 Ligamentum internum, callo parvo sustentutuni. 



This species is thin, convex, inequihxteral, a little higher than long, perpendicularly 

 truncated in front, rounded behind and along the ventral margin. The front dorsal line 

 is horizoual and straight, and at the termination forms a sharp angle with the anterior 

 side. The posterior dorsal edge is rather oblique and nearly rectilinear. The valves are 

 dirty whitish, dull, somewhat pearly within, everywhere finely granuhu', and also sculp- 

 tured with many (about fifty) fine hair-like raised lines and a few concentric lines of 

 growth at intervals, distinct and almost lamellar. The umbones are somewhat incurved, 

 and directed towards the front. The lunule is concave, smooth, extends to the end of 

 the dorsal margin, and is entirely in the right valve. It projects a little beyond the level 

 of the rest of the margin of the valve, and fits into a slight emargination in the corre- 

 sponding part of the left valve. The hinge-line is altogether destitute of teeth, and the 

 ligament is internal and supported by a small shelly ossicle underneath. The front 

 adductor scar is high up, just under the front dorsal margin, the posterior one being lower 

 down, at the end of the dorsal slope. 



Length 19 mm., height 20, diameter 14. 



Habitat. — Station 106, Mid Atlantic, in 1850 fathoms; Globigerina ooze. 



The preserved animal of this fine species appears to agree very closely with the 

 description of Lyonsiella by Sars in Eemarkable Forms of Animal Life, p. 25. 



It has a single branchial plume on each side, no labial palps, and a byssiferous foot. 

 The anal and branchial siphonal orifices are distinct, the latter being surrounded by papillae. 



Lyonsiella 2'xipyrcicea, n. sp. (PI. XXV. figs. 2-21)). 



Testa magna, tenuissima, alba, rotunde cordata, globosa, liris filiformibus numerosis 

 radiantibus ornata, incrementi lineis tenuibus sculpta, epidermide tenuis.sima sordide 

 albida induta. Umbones prominentes, antemediani, valde incurvati, antrorsum versi. 

 Linea cardinalis edentula, tenuis. Ligamentum internum, parvum, paulo pone umbones 

 situm, callo crassiusculo sufFultum. Pagina interna nitida, submargaritacea, radiatim 

 striata, striis cum liris externis congruentibus. 



(ZOOL. CHALL. F.XP. — PART XXXV. 188.5.) Mill 10 



