88 



CRUSTACEA CIRRIPEDIA 



CHAP. 



x 1. 



(Mter i)ain.f' 



of them, e.g. Oxynaspis, live at considerable depths attached to 

 T corals, etc., but large numbers float on the 



surface of the sea, fixed often on logs and 

 wreckage of various kinds. Dichelaspis 

 is found attached to the shells of large 

 Crustacea. 



Cotirhoderma is an interesting genus, 

 the species of which live affixed to various 

 floating objects, the keels of ships, etc. ; 

 the mantle is often brilliantly coloured, 

 as in C. rirgata, and the skeletal plates 

 are reduced to the merest vestiges, leaving 

 the greater part of the body fleshy. 



Fam. 3. Tetraspidae. This family 

 includes the single genus Ibla (Fig. 58), 

 which possesses only four skeletal plates, 



FIG. 57. Conchodenna vir- * 



G, Carina ; a pair of tcrga and of scuta, coloured 



blue, while the peduncle is covered with 

 brown spines. There are only two very 

 similar species known, /. ciimingii, which is found attached to the 



peduncle of Pollicipes 



mitella, and I. qna- 



</riralvis, living on 



masses of the Siph- 



onophore Galeolaria 



decumbens. These two 



species are quitediffer- 



ent in the partition 



of the sexes. In /. 



cumingii the large 



individuals of normal 



structure are females, 



inside the mantle- 

 cavities of which are 



attached dwarf males 



of the form shown in 



Fig. 59. 



These organisms 



have the peduncle 

 buried completely in the substance of the female's mantle, inside 



-T 



E- - 



FIG. 58. Ibla cumingii, 

 9 , x 1. S, Scutum ; 

 T, terguin. (After 

 Darwin.) 



FIG. 59. Ibla cumingi-i, ilwaif 

 male, x 32. A, Antennae ; 

 Ji, part of male imbedded 

 iu the female, to which the 

 torn meniln-ane M Belongs ; 

 JE, eye ; Th, thoracic ap- 

 pendages or cirri. (After 

 Darwin.) 



