PNEUMODERMATIDAE 



291 



fort ' of an oval shape, two pointed denticles on each side, and a fold or suture without 

 cusp in the middle line. This fold indicates the place where the two median teeth of the 

 larva join to form one central tooth in the adult. It often breaks into two halves and I 

 even think that one half sometimes persists in some rows, while the other disappears, 

 this median tooth being inclined to disappear altogether as it does in the genus Pneiimo- 

 derma. This fact explains the asymmetry of the tooth in my Monaco specimen." 

 Mme Pruvot-Fol has been so good as to send me drawings of the radula of the above 



Fig. I. 



Spongiohranchaea intermedia, Pruvot-Fol. a, median tooth; b, first lateral tooth (from original Monaco 



specimen). 

 Spongiohranchaea intermedia var. c, median tooth on same scale as « ; </, two median teeth (halves) ; e, lateral 



teeth, I row;/, mandible;^, one median tooth; h, two median teeth (halves);/, the first lateral teeth of 



two rows. (Figs. », h,] more highly magnified than preceding figures.) 



specimens and also of the Monaco example for comparison (Fig. i). The most important 

 difference between the Discovery specimens and the type is that both Mme Pruvot-Fol 

 and myself counted nearly eighty suckers on an expanded arm, whereas in the type only 

 sixteen were counted; owing, however, to the type specimen being contracted, and the 

 possibility that a few suckers had been lost during dissection, the number might have 

 been twenty or more. As Mme Pruvot-Fol points out, there is great variability in these 

 organs. It is a curious fact, too, that the suckers in the type (which measured 17 mm. 



