214 PAUEONTOLOGY OF NEW-YOEK. 



Plate XLVIII. 



Fig. 4. A fragment of a largts spocimen, composed of twenty or more chambers, one side of which is 

 worn down, exposing the siphuncle, which contains the embryo tube, within which is a 

 young shell a. 



Fig. 4 b, b. The larger or embryo tube, which is broken at the lower extremity. 



Fig. 4 e. The siphuncle, the space surrounding the tube being filled with calcareous spar. This specimen 

 shows, in a very satisfactory manner, the position of these tubes within the parent shell. 

 Unfortunately we have not yet been able to obtain the apex of one of the larger shells, to 

 determine whether the siphuncle continues of the same dimensions throughout. A small 

 portion of the upper part only of the embryo tube is preserved in this specimen. 



Fig. 3. An embryo tube with a longitudinal section on one side, showing a slender septate tube within, 

 which is nearly destroyed by weathering. 



Fig. 2. A similar tube, free from striae, and like the others. This tube has been broken at a, b, c ; and 

 the transverse sections a, b, e, at the bottom of the plate, represent its appearance. The 

 outer tube contains an inner one, which is septate throughout its entire length, and furnished 

 with an excentric siphuncle, which is distinctly represented in the section a. An e.xposure of 

 the surface of this septate tube shows precisely the same sculpture as that represented in the 

 specimens 2 and 3 of plate 45, and also the small enclosed tube fig. 5 of the same plate. 



Fig. 1. A separate embryo tube, nearly perfect, and showing some inequalities near the base, apparently 

 from contact with the inner side of the siphuncle. 



Plate XLIX. 



Fig. 1 a. Ventral side of a fragment, showing the siphuncle, which is worn through in the lower part, 

 showing the smooth embryo tube. This specimen shows the more abrupt arching of the 

 septa as they approach the siphuncle. 



Fig. 1 b. A fragment, preserving the embryo tube. 



Fig. 1 c. Trnnsverse section of the last, which is slightly elliptical from compression. The embryo tube 

 is pressed against the upper side of the siphuncle, the outline of which is only faintly re- 

 presented. 



Fig. I d. A similar fragment, embracing a portion of the embryo tube. In this one the septa are a little 

 more approximate than in the other specimens, but it docs not difl^er in other respects. 



Fig. 1 e, A nearly perfect embryo tube, with a few of the septa of the parent shell still attached. 



The tenacity with which this tube retains its connexion with the parent shell, as shown 

 in all these fragments, and particularly the last one where the outer shell is nearly destroyed, 

 would indicate something more than accidental possession of the siphuncle. In all these 

 specimens, the septa are distant one fourth to one sixth the diameter of the outer shell. 



Plate L. 



Fig. 1 a. An embryo tube containing a young shell. This specimen is more elongated, and less rapidly 

 attenuating than the prevailing forms of the species. The outer tube is smooth, while the 

 inner one is striated ; but the crystalline condition of the rock renders it difficult to determine 

 the character of the tubes with accuracy. 



Fig. 1 b. This tube is more slender than the usual forms, but does not difl^er in other respects. 



Figs 2 a, b. Fragments of smooth embryo tubes, apparently of the same species, differing only in being 



