MALE. 199 



exact size relatively to the mandibles ; the outer maxillae 

 have the same, quite peculiar pointed outline, and the 

 olfactory orifices are tubular, and hold the same unusual 

 position. It is most rare to find so close a resemblance 

 in the parts of the mouth, except in very closely allied 

 genera, and often species of the same natural genus 

 differ more. Again, in the long oesophagus and con- 

 stricted stomach there is a resemblance to Ibla. In the male 

 of Ibla quadrivalvis, the caudal appendages are multi- 

 articulate ; now, this is a character confined to four genera, 

 namely, Ibla, Alepas, Pollicipes, and Lithotrya. I may 

 add, that large tubular olfactory orifices are confined to 

 the same genera, together with Scalpellum. Lastly, it 

 particularly deserves notice, that the prehensile antennae, 

 in having a hoof-like and pointed disc, with a single spine 

 on the heel, much more closely resemble these organs in 

 Scalpellum, certainly the nearest ally of Ibla, than in any 

 other genus ; they differ from the antennae in Scalpellum, 

 only in the ultimate segment not having a notch on one 

 side. These organs, unfortunately for the sake of com- 

 parison, were not found in the female and ordinary form 

 of Ibla. The full importance of the above generic resem- 

 blance in the antennae, will hereafter be more clearly seen, 

 when their classificatory value is shown in the final dis- 

 cussion on the sexual relations of Ibla and Scalpellum. 



Here, then, we have a pedunculated Cirripede very 

 much nearer in all its essential characters to Ibla than to 

 any other genus, and exclusively of the male sex ; and this 

 Cirripede in six specimens, from two distant localities, 

 adhered to an Ibla exclusively of the female sex. May 

 we not, then, safely conclude that these parasites are the 

 males of the Ibla Cumingii ? Considering that, in the same 

 class with the Cirripedia, there is a whole family of crus- 

 taceans, the Lerneidae, in which the males, compared with 

 the females to which they cling, differ as much in appear- 

 ance as in Ibla, and are even relatively smaller, I should 

 not have added another remark, had there not been under 

 the head of the following species, and of the next genus 



