365 



deep and nearer the autisiphoual side; siplional projection of lip ratker 

 long and linguiform, while that of the dorsal side is nearly semicircular in 

 outline. Surface entirely smooth, or with only obscure lines of growth, 

 curving parallel to the projections and sinuses of the lip. 



Septa moderately approximate but not crowded; lobes and sinuses on 

 opposite sides of the shell sometimes differing slightly in their details. 

 Siphonal lobe shorter than the first lateral, and a little more than one- 

 third wider, provided with two rather large, widely-separated terminal 

 branches, with each about six or seven small, short, unequal subdivis- 

 ions, some of the larger of which are bifid and others trifid. First lat- 

 eral sinus of about the size of the first lateral lobe, and divided at the 

 extremity into two short, subequal, trifid, terminal branches, with 

 sinuous and obtusely digitate margins. First lateral lobe a little 

 longer than, and about as wide as, the first lateral sinus; on one side of 

 the shell sometimes ornamented by five short, n'early equal, palmately- 

 spreading branches, with from four to five digitations each (see fig. 2 c), 

 Vhile on the other it is sometimes divided at the extremity into four 

 unequal branches (see fig. 2 &, plate 4), one of which is considerably 

 longer than the others, and more or less distinctly bifid and digitate. 

 Second lateral sinus of nearly the same size and form as the first. 

 Second lateral lobe a little shorter than the siphonal lobe, and about 

 two- thirds as wide, nearly equally divided at the extremity into two 

 short, spreading branches, of which the one on the siphonal side is pro- 

 vided with four short, unequal, digitate subdivisions, and the other into 

 two very unequal branchlets, the larger of which has four or five digi- 

 tations. Antisiphonal lobe about half as long as the adjacent side of 

 the second lateral lobe, near half as wide as long, and ornamented by 

 four or five digitations on each side. 



The largest fragment in the collection measures 1.4:9 inches in its 

 greater diameter, and 1.13 inches in its smaller, and, judging from its 

 very gradual taper, it appears to have been, when entire, as much as 12 

 or 15 inches in length. 



At the time I proposed the name B. inornaius for this species, I only 

 knew Dr. Trask's B. CMcoensis from his figures and description of a 

 very small specimen, giving scarcely any idea of the septa of what is 

 now known to be a very young individual of his species. Since seeing 

 Mr. Gabb's figures of the larger specimens of the same shell from the 

 original locality, I am led to think that our Sucia Island specimens may 

 belong to the same spe'cies. Of this, however, I cannot be positively 

 sure without a better series of specimens for comparison, particularly 

 as our specimens differ somewhat in the details of their septa from Mr. 

 Gabb's figures, and are still considerably larger than those illustrated 

 by him. In its septa, it agrees more or less nearly with B. graiidis, H. 

 and M., and B. ovatus, Say, but it seems never to attain a size approach- 

 ing that of the adult shell of either of these forms, while it is destitute 

 of the lateral undulations of the same, so far as can be determined from 

 our specimens, though Mr. Gabb figures one individual that he refers 

 to Dr. Trask's species with these undulations well developed. It is 

 worthy of note, however, that his specimen showing this character dif- 

 fers materially in other respects from our specimens, as well as from the 

 otlier referred by him to the B. Chkoensls. 



Locality and i)os'itlon. — Cretaceous of Sucia Islands. 



