Mr. J. E. Gray on the Animal of Spirula. S59 



of the skin it appears as if this shell was covered with a skin when 

 the animal is alive, and that the exposure of the surface of the 

 shell has only been caused by the contraction of the animal, and 

 especially of the skin over the shell, from the animal having been 

 placed in very strong spirits when it was first caught. The shell 

 is placed symmetrically, the larger part being on the hinder part 

 of centre of the back and the smaller whorls below on the hinder 

 part of a line drawn down the centre of the lower or anal surface of 

 the mantle ; the extremity of the body behind the shell is rounded 

 and covered with a large, round, rather thick gland with a circular 

 central cavity, and the line between the gland and the mantle is 

 covered with sandy particles probably attached to this place by 

 the secretion of the gland, and these particles are most abundant 

 on the side near the skin covering the shell. 



In this specimen, which has been preserved in spirits, the head 

 and arms are reddish with a multitude of minute rusty spots ; 

 the mantle is nearly uniform pale yellowish, and the gland at 

 the end of the body is uniform reddish brown. It is to be ob- 

 served that the shell in this animal is placed on the animal in 

 the normal position, that is, on the dorsal surface of the body, 

 with the spire bent towards the ventral sides, as in almost all 

 other Mollusca but the Nautilus and the Patella. 



The mantle is free from the body on all sides at its oral edge, 

 and without any cartilaginous ridges ; this edge is formed into 

 a point on the centre of the dorsal aspect, and into two mesial 

 processes, one situated on each side of the anal funnel on the ven- 

 tral side ; the funnel is quite free from the mantle. 



The part of the shell which is exposed is covered with minute 

 rugosities and indistinct reticulations, somewhat like the surface 

 of a cuttle-fish bone, as figured in ' Ann. Sci. Nat.' 2nd series, 

 xvii. 1. 11. f. 9, 10. 



I am informed by M. Clausen that he had several specimens 

 of this animal alive, and kept them some time in a vessel filled 

 with sea-water, and that they had the power of ascending and 

 descending at pleasure. 



The Spirula will constitute a group of the DecapodousCephalo- 

 pods, forming a passage to the Ociopodidce ; for, like the latter, 

 they are entirely destitute of any dorsal fins, and well-charac- 

 terized by the presence of a regularly chambered internal shell, 

 furnished with an internal marginal siphon. 



The examination of this animal confirms me in the opinion 

 which I expressed in the ' Synopsis of the British Museum' (1840, 

 p. 149), that the Ammonites, from their texture and the small size 

 of the last chamber, are internal shells, and should be arranged 

 with the Decapodous Cephalopods, being chiefly distinguished 

 from the Spirula by the siphon being always on the dorsal mar- 



