SttoS 



9-10 



238 SCALPELLUM VULGARE, 



The importance of the following measurements (in frac- 

 tions of an inch) will hereafter be seen. 



Length of whole organ, from end of disc to the further \ 3s . 3s 



margin of the oblique basal articulation . . j BoDO 



Length of whole organ, to the inner margin of the oblique \ , 



basal articulation . . . J B3 

 Breadth of basal segment, measured half-way between the i 

 basal and second articulations, — the limb being viewed I 

 from vertically above . J 

 Length of hoof-like disc, measured from the apex to the 1 



middle of the articulation with the basal segment J 6o ^° 



Breadth of ditto ..... 5505 



Length of ultimate segment . g^o 



Breadth of „ beneath the notch . . 55 7 m 



Breadth of „ above the notch . . ^ m 



I did not see the cement-ducts, which, perhaps, was 

 owing to the corium extending from the inside of the 

 whole animal some way into the antennae, thus rendering 

 them rather less transparent than in common Cirripedes. 

 That the ducts and cement-glands exist, is certain, for the 

 antennae in every case were enveloped in a little irregular 

 mass or capsule of the usual, brown, transparent, lami- 

 nated cement. When several of these parasites were 

 attached close together, the cement ran up between them. 



I may here state, that I found on one Scalpellum, three 

 males very lately attached, and not as yet imbedded in 

 the chitine border; they were white, opaque, pulpy, and 

 full of oily globules ; the lower part was considerably 

 more pointed, and extended further beyond the prehensile 

 antennae, than in the older and imbedded specimens. 

 There were distinct remnants of two great reddish-brown 

 eyes, showing that in this respect the larvae of the male in 

 their last stage of development, are characterised like the 

 larvae of other Lepadidae. The male larva would, pro- 

 bably, be a little larger than the male itself; but yet 

 compared with the larva in the earliest stage, there can 

 have been unusually little increase of size during the 

 several intermediate metamorphoses ; I judge of this from 

 the dimensions of the larva of the hermaphrodite in the 

 first stage, namely, ^ths of an inch, exactly the size of 

 some of the smaller males. In the allied genus lbla, 



