UTRICULUS. 427 



This little creature is bold^ and crawls rapidly. The 

 absence of eyes is a remarkable character; and there 

 can be no question of the fact^ so far as the best optical 

 ^instruments^ long and patient examination under the 

 most favourable circumstances_, and the concurrent tes- 

 timony of three practised observers (Mr. Waller^ Mr. 

 Peachy and myself) can establish it. Living specimens 

 of U. expansus and U. hyalinus were placed side by side, 

 and fully displayed themselves. The latter had distinct 

 eyes at the base of the tentacles, outside the shell. 

 The other, which was three times as large and equally 

 exposed to view, showed no trace of eyes anywhere, al- 

 though it was carefully examined in every position, in 

 order to detect them. They could not have been sub- 

 cutaneous ; because the tissues of the animal were almost 

 transparent, and I used a high microscopic power, by 

 means of which the internal structure was clearly 

 seen. Similar anomalies in respect of these so-called 

 visual organs occur in the genera Eulima, Natica, and 

 Pleurotoma among our native mollusks. 



6. U. iiya'linus"^, Turton. 



Bulla hyalina, Turt. in Mag. N. H. vii. p. 353. Amphisphyra hyalina, 

 F. & H. iii. p. 521, pi. cxiv. d. f. 1, 2, and (animal) pi. Utl. f. 2. 



Body white, with a faint tinge of brownish-yellow : liead 

 large and broad, deeply cloven or bilobed in front : tentacles 

 triangular, flanking the head, folded back or carried erect at 

 the will of the animal : eyes very small, but distinct and black, 

 widely separated ; when the animal is crawling they are out- 

 side the shell, some way behind the head ; when it is at rest 

 this part of the animal is to some extent withdrawn, and the 

 eyes are seen through the front of the transparent shell: 

 foot oblong, rounded in front (where it is broader than in the 

 middle), and unequally forked behind, like the tail of a shark : 

 gill-plume pale yellow : ovary brown. 



Shell cylindiic-oval, dilated in the middle, and nearly 



