88 



CRUSTACEA CIRRIPEDIA 



c 



Fig. 57.— Conchodenna vir- 

 gata, x 1. C, Carina; 

 S, scutum ; T, tergurn. 

 (After Darwin.) 



of them, e.g. Oxy^iaspis, live at considerable depths attached to 

 -J- corals, etc., but large numbers Heat 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. 



Conchoderma is an interesting genus, 

 the species of which live affixed to various 

 floating objects, the keels of ships, etc. ; 

 the mautle 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 Ihla (Fig. 58), 

 which possesses only four skeletal plates, 

 a pair of terga and of scuta, coloured 

 blue, while the peduncle is covered with 

 brown spines. There are only two very 

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



peduncle of Pollicipes 



mitella, and I. qua- 



drivalvis, living on 



masses of the Siph- 



onophore Galeolavia 



decumhens. These two 



species are quite differ- 

 ent in tlie 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 



liave the peduncle 

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



Fia. 58. — Ibla cumingii, 

 9 , X 1. ,S', Scutum ; 

 T, tergum. (After 

 Darwin.) 



M 



Fia. 59. — Jbla cumingii, dwarf 

 male, x 32. A, Antennae ; 

 B, part of nnile imbedded 

 in tlie female, to which the 

 torn membrane M belongs ; 

 .fi", eye ; Th, thoracic ap- 

 pendages or cirri. (After 

 Darwin.) 



