180 GENUS IBLA. 



wise bisexual : but after the facts presently to be revealed 

 regarding the sexes in Ibla and Scalpellum, it is quite 

 possible that the male and female organs may be developed 

 in inverse degrees in different and adjoining individuals. 

 The genus Anelasma is, I think, properly placed be- 

 tween Alepas and Ibla. In several of its characters, such 

 as the absence of calcareous valves, the broad blunt end 

 of the peduncle, the spineless cirri, the small size of the 

 tropin, and more especially the absence of transverse striae 

 in those muscles, which in mature cirripedes are thus 

 furnished, we see that this genus is in some degree in an 

 embryonic condition. 



Genus — Ibla. Pis. IV, V. 



Ibla. Leach. Zoolog. Journal, vol. ii, July, 1825. 



Anatifa. C-uvier. Mem. pour servir, Mollusques, Art. 



Anatifa, 1837. 

 Tetkalasmis. Cuvier. Regne Animal, 1830. 



(Fcem. et Herm.) Valvce 4, cornece : pedunculus spinis 

 cornets, persistentibus vestitus. 



(Fern, and Herm.) Valves four, horny: peduncle clothed 

 with persistent, horny spines. 



Body partly lodged within the peduncle ; mandibles 

 with three teeth ; maxillae with two obscure notches ; outer 

 maxillae pointed ; olfactory orifices prominent ; caudal 

 appendages multiarticulate. 



Male and Complemental Male, parasitic within the sack 

 of the female or hermaphrodite ; mouth and thorax seated 

 on a long tapering peduncle, but not enclosed within a 

 capitulum ; mouth with normal trophi, but palpi small and 

 almost rudimental ; cirri ruclimental, reduced to two pairs ; 

 penis reduced to a pore; caudal appendages rudimentary. 



Attached to fixed littoral objects : Eastern Hemisphere. 



General Remarks. — As there are only two species as 



