67 



CHAPTER XII. 



SIPHONS. — THE ARCTIC CYPRINA. — THE LITTLE CIRCE. — ASTARTE. 



ISOCARDIA COR, — THE PRISONER. 



CYPBINID^. 



HiTHEETO we have spoken of the siphonal tubes being long 

 or short, divided or united, fringed or plain; but, in the 

 present family, the tubes are hardly properly so called, for 

 they do not (or scarcely) protrude beyond the body : some of 

 them are mere openings. This is connected with a character 

 in the shell. The impressed Hue, which passes from one 

 muscular impression to the other, is in the preceding fami- 

 lies more or less curved at the back into a sinus ; but in this 

 family it has no such curve. In proportion to the length of 

 the siphons, is the depth of sinus in the impression of the 

 mantle ; and when the siphons do not at all protrude, the 

 sinus is not there. This character, although one of degree, 



