JOURNAL OF CONCHOLOGY, VOL. 9, NO. IO, APRIL, I9OO. 



Methods of Progression. — Usually the shell is dragged along 

 the ground after the animal, though more rarely it is lifted to a hori- 

 zontal position (fig. 1 a). On two occasions 

 I observed the animal protrude its head 

 under the shell towards the spire and pro- 

 gress in that direction, forcing the shell 

 along the ground in front of it, apex first, 

 and then lift the shell over its head at an 

 angle of about 45 degrees and continue its 

 march in that position (fig. ib). The pro- 

 gression is always by slow jerks, and not a 

 continuous glide. I have not observed the 

 shell carried in the position of Jeffreys' 

 figure (B.C., vol. i., pi. vii., fig. 18), though Nilsson says "the animal 

 sometimes carries its shell erect, but generally drags it along depressed." 



Texture and Form of the Animal. — I was much struck with 

 the extremely flexible and elastic nature of the animal. I have 

 observed one emerge from the shell as it lay flat on a horizontal sur- 

 face, and make a complete circle with its head and tail, without 

 moving the shell. It is also remarkable how far the animal will 

 protrude from the shell, and how slender an attachment connects the 

 head and foot with the part within the shell. The end of the tail is 



often curled up. Along 

 the neck and down the 



Fig. 



C cecii ioides acictcla. 



Ctecilioides acicula, showing mucus groovt 

 head and tail. 



-^y^//^ \ \ \ VVVVs J>^br— front of the head are two 



mucus sulcations on 

 either side of the dorsal 

 line (fig. 2b). The tail is 

 pointed and sharply carinated; from the dorsal ridge mucus sulcations 

 descend to the lower edge (fig. 2a). 



Eyes and Tentacles. — Jeffreys' enlarged figure (B.C., vol. i., pi. 

 vii,, fig. 19) is not quite accurate. He seems to have taken his descrip- 

 tion from Nilsson, and it may be doubted whether Jeffreys himself 

 examined the animal with sufficient care. Nilsson had evidently 

 studied the animal, but he was not correct in describing the upper 

 tentacles as " not thickened." In all the specimens that I have 

 observed the upper tentacles are certainly slightly bulbous when fully 

 or nearly fully extended, though this does not appear when they are 

 only slightly protruded. Nilsson, however, correctly remarks that the 

 apices of the upper tentacles are not ' marked with a black spot.' 

 Now Lamarck (to whom Nilsson refers) seems to have been the only 

 one to observe the colourless eyeballs, and he did not recognise them 

 as such. Nilsson says (quoting Lamarck) 1 : " In this species no eyes 



1 Hist. Moll. Svec. Terr, et Fluv., p. 39. 



