212 



PALiONTOLOOY OF NEW-YORK. 



Plate XLVI. 



Fig. 1 a. A fragmont 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 A. 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 e. 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 XLVIL 



Fig. 4 o. A fragment from the apex of one of these tubes, which is septate as in the larger specimens. 

 Fig. 4 A. 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 e. A fragment of a similar young shell, where the lamellose strisB have become vesicular, giving 

 a rough scaly appearance to the surfaca 



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 

 sliells, are all identical ; some of therh 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 o). There is a slight diflference 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. 

 litieolatum, as well as other species of Okthoceras, is variable. In the small specimens with 



