212 
PALAEONTOLOGY OF NEW-YORIC. 
Plate XLVI. 
Fig. 1 a. A fragment of the parent shell, enclosing an embryo tube within the siphuncle. The young 
shell within this tube is marked precisely as fig. 4 a, pi. 45. 
Fig. 1 b. Transverse section of the last, showing the large lateral or excentric siphuncle of the old shell. 
The shell is crushed, as shown in the upper figure, so that a perfect section cannot be 
given. 
Fig. 1 c. The surface marking of the young shell, enlarged. 
Fig. 2 a, b. The external shell, and a longitudinal section of a young shell, which is destitute of septa. 
Fig. 3. This is marked upon the surface as other specimens of the var. lineolatum. The septa in the 
figure are erroneously represented by the engraver much nearer than they are in the 
specimen. 
Plate XLVII. 
Fig. 4 a. A fragment from the apex of one of these tubes, which is septate as in the larger specimens. 
Fig. 4 b. A transverse section. 
Fig. 4 c. A fragment which is annulated near the apex, and septate to the extreme point. 
Fig. 4 d. Section near the apex. 
Fig. 4 c. A fragment of a similar young shell, where the lamellose striae have become vesicular, giving 
a rough scaly appearance to the surface. 
I have given so great a number of figures of this variety, in order to show the various 
forms and aspects under which it appears. The separated and enclosed tubes, or young 
shells, are all identical ; some of them being septate, and others without septa. It is im¬ 
possible to determine when these bodies assume the septate character, or whether they are 
always so except when the septa are removed by accident; which may be the explanation 
of their absence in larger tubes, while they are present in smaller ones as I have shown in 
the preceding figures. 
277. 9. ENDOCERAS PROTEIFORME, var. STRANGULATUM. 
Pl. XLVI. Figs. 4 a, b, c, d e. 
It is not entirely certain that the character on which this variety is founded does not 
exist in the var. lineolatum ; since, in all the specimens of that one examined, the outer 
chamber is not preserved. The surface markings are precisely similar in the two ; some 
specimens being quite destitute of longitudinal striae, while in others they are faintly 
preserved, and the surface resembles the var. tenuistriatum. The distance of the septa is 
from one fourth to one third the diameter of the tube, corresponding closely with those of 
the var. tenuitextum (PI. xlv, fig. 3 a). There is a slight difference in this character in 
the two specimens figured, but the parent shells are also shown to be somewhat variable in 
the distance of the septa. The position of the siphuncle in the best preserved specimen is 
nearly central, while in another specimen it is somewhat excentric. In this respect, the var. 
lineolatum , as well as other species of Orthoceras, is variable. In the small specimens with 
