l-i'llNn* HI!' >V 



N i ii N- < 'arpenter. I'n >/" /'"'. 



11 small, whitish, tinned \vitli rOMafte; valv- gi.thic-arched, 



mi suharute; entire surface minutely irranulnse: lateral 



-picii'Misly il. -lined, having strong diagonal and sutural 



; with well projecting rounded grains; end valves hav- 



ini: -uhohsolete radiating riblet>: central areas having about s di. 



taiit, raised subgranulose longitudinal rihs on each side, the rih< 



at the jugum : inter.-ticcs latticed with suhradiating rihlct-: 



umhnnes conspicuous, the uinhonal margin deeply toothed by a wart- 



bearing ril>. the teeth 8 to 10, obsolete toward the jugum : margin 



ly intortrd. Tnibo of posterior valve submedian. slightly j >ro- 



iiaririn elegantly pectinated. Interior: sinus large, Hat. 



: rate : insertion-plates acute, broadly uniiissate. end 



s having about 8 slits ; eaves conspicuous. Girdle having lar^- 



riated scales. 

 Length 61, breadth 2-1 mill. ; divergence 90. (Cj^r.} 



,! /xA//td, 20-30 fins. 



veredentiens CPR., Rep. Brit. Asso. Adv. Sci. 

 p. 'il!*: I 'roc. C'al. Acad. Sci. iii, p. 211. 



A small arched species, sculptured like /. mertensii, but with two 

 8, one of which dentates the sutures. The girdle scale- 

 rat her large, flattened and striated, as in typical I&knochiton. 



I. BBRRATUB ( 'arjicnter. Utifiyured. 



Shell small, ashy, dotted here and there and especially at the 

 suture- with olive, sometimes spotted with red ; oval, suhdepressed, 

 the sutures indistinct; entire surface mo.-t minutely granulated: 

 lat'-ral areas strongly defined, provided with two to five very wide, 

 obtuse rihs, no interstices; posterior margins elegantly serrated. 

 Central areas having about 12 acute parallel ribs on each ride; 

 juLrum obtuse, scarcely uinhonate: with subradiating latticing ribs. 

 intei>tiees impre.-sed. Mucro median, obtuse. End valves having 

 about 20 obtuse rihs, like the lateral areas. Interior: median 

 valves bifi>sate, end valves with about !> .-lit-. Sutural plates i 

 liirdlc imbricated with large, scarcely >triated .-cales. 



Length 8'. breadth ~> mill. ; divergence 115. (<> r -) 



Caj" >V. /. ' 'fiwritin. 



Ischnochtion terratut CP&.I Ann.iV Mai r . Nat. Hist. (3) xiii. p. 



