i894 CEPHALOPOD BEGINNINGS. 427 



should, at least for a time, turn the scale in the direction of its am- 

 monite affinities. To this argument Branco added the fact of its 

 resemblance to the young of Mimocevas compycssnni and the presence of 

 a dorsal lobe in the suture-line. This leads us straight to the recent 

 observations of J. M. Clarke. 



At various localities in Ontario and Livingstone counties, New 

 York, at a horizon corresponding with that of the German Bactrites, 

 Clarke has found numerous specimens, representing three or four 

 species, of straight cephalopod shells, all possessing protoconchs. 

 Some of these he refers to the genus Bactrites (7), while another 

 he prefers to regard as Orthocems (6). 



Concerning Bactrites, Clarke is doubtful, whether the specimens 

 described by Branco were really of this genus ; but he is convinced 

 that his own material " corresponds, even to its specific characters, 

 with that upon which the genus was established." Assuming 

 the correctness of Branco's reference, the descriptions now given 

 by Clarke supplement and in some respects set right those of 

 Branco. The protoconch of the American specimens is not 

 ovoid, but " bubble-shaped, frequently a little unsymmetrical or 

 directed to one side, very broadly sessile upon the end of the 

 shell tube, from which it is separated by a sharp constriction " 

 (Fig. I, a). The position of the siphuncular passage, even in the 

 first septum, is distinctly lateral (Fig. i, b). Where the siphuncle 

 passes through the septa, it is surrounded by backwardly directed 

 siphuncular collars or ' septal necks,' These septal necks are often 

 so inclined as to be attached to the shell-wall, so that when the shell- 

 wall is removed, the outer portion of the neck is almost invariably 

 carried away with it. Thus an apparent dorsal lobe is formed 

 (Fig. I, d) ; and it is on this lobe, which does not really exist, 

 that Branco has based some of his argument as to the affinities of his 

 specimens. 



The specimen referred by Clarke to Orthoceras is briefly described 

 (Fig. 2, a, b). " It consists of the first or apical chamber of the shell, 

 to which the protoconch is attached. The upper end of the specimen 

 shows the first septum (not counting the ' apical plate ' separating 

 the protoconch from the first chamber) to be circular and with a 

 central sipho. The lateral walls of the first chamber taper rapidly 

 to the plane of conjunction with the protoconch and its depth 

 is about one-half that of the latter. The protoconch itself is semi- 

 ovoid in shape," and tapers slightly towards the apex as does that of 

 Belemnites. It is of large size, as compared with the protoconchs 

 of Orthoceras described by Hyatt, and " shows no indication of 

 shrinkage or other irregularity, and its distal extremity is] perfectly 

 smooth." The specimen is referred to Orthoceras because the 

 siphuncle (as shown in Fig. 2, a) passes through the centre of the 

 first septum, and is not lateral as in the associated specimens of 

 Bactrites. Larger specimens referred to Orthoceras, but without 



