322 Proceedings of the Royal Physical Society. 



head ; on its dorsal wall, immediately behind the aperture, 

 are two low cushion-like papillae in the middle line, and 

 behind these three long-pointed papillse arranged in a triangle 

 with the apex directed forwards. 



The Head. — The head proper is small, much smaller than 

 either of the enormous globular eyes, which occupy the whole 

 of its two lateral surfaces. 



The Arms. — The sessile arms are short, on an average about 

 one-third the length of the body ; their order of length is 

 3, 2, 1, 4 ; a toothed membrane extends along the arms, but 

 forms only a very small web between them. They are 

 furnished with two rows of suckers most numerous and 

 closely packed on the dorsal arms. The suckers are sub- 

 globular, the proximal half of the globe being opaque and 

 muscular, the distal corneous and semi-transparent. The 

 suckers on the dorsal and ventral arms are subequal, and 

 also on the lateral arms for the proximal half of their length; 

 on the third quarter are situated about eight large suckers, 

 whose diameter fully equals that of the arms ; on the terminal 

 fourth the suckers gradually diminish. The margin of the 

 larger suckers is almost entire but marked out into irregular 

 very shallow, square-cut teeth ; on the distal margins of the 

 smaller suckers the teeth become more prominent, but are 

 blunt, and about 8 to 10 in number. The tentacles are but 

 little longer than the arms, and only slightly expanded at 

 their extremities. On the inner side of the stem is a groove 

 which bears two and afterwards four irregular rows of very 

 minute suckers, among which are a number of fixing-cushious 

 {Hoiftepuder, Steenstrup). On the club are four rows of 

 suckers about as large as the smaller ones on the arms; 

 their horny rings are provided on the proximal semi-circum- 

 ference with about fifteen closely set sub-acute teeth, while 

 the distal semi-circumference bears about nine long very 

 acute teeth. 



The Shell. — The pen is long, narrow anteriorly, expanded 

 in the posterior half, and forming a hollow terminal cone 

 enclosing part of the genital gland. 



