- -Ip.d - 



Shell larp-e, su'btrapezoidal, the length more than one and 

 one-half times the height, inflated; um'oones relatively low and 

 flat, strongly hent forward, sitiiate^ at almost the anterior third 

 of the length; angle between antero-dorsal and ant ero- lateral r.iar- 

 gins ahout 90*^, that "between postero- dorsal and postero-lateral 

 margins about 130°; anterior lateral margin ronrided; posterior 

 lateral margin obliquely truncated above and prorluee- below; post- 

 erior half of ventral margin subparallel to the dorsal margin, 

 anterior '^ alf gently arcuate; e'temal sculpture the same as on 



the typical halidonata ; cardinal area, hinge and interior mar- 

 gin as in halidonata . 



Dimensions .- Length, 70 mm.; alt., 44 mm.; semidiara. , 21 

 ram. ; length of hirjge-line, 52 mm. 



P.emarlrs . - It is here proposed to consider Area consobrina 

 Souerby a variety of A, halidonata Dall. Althouj?h Sowerby's des- 

 cription is brief and inadequate, the accom"panying figure is satis- 

 factory so that there is little doubt as to the salient features 

 of his consobrina . Unforttmatelj , hov7ever, as Dall has pointed 

 out (1), consobrina had been used in 1844 by d'Orbigny (2) for a 



fl). Trans, '''agner Free Inst., Sci., Philadelphia, vol. S, v>t, 

 4, p. 647, 1338. 



(2). Pal. ^rancaise, f Terraine Gret.) vol. 5, op. 209-210, -ol. 511, 

 figs. 4-7, 1844. 



