SUPER-ORDER IV 



rih'IUPKDlA 



Lepas, Linn. (Fig. i:w:ij. Peduncle naked. Capitnlum r,>nsi-tin^ !' nly t\v., 

 very large triangular scuta, two small trrga, and a single carina. IMion-m- and Recent 



Poecilasma, Darwin. Capitulum 

 consisting of three, five, or -evi-n 

 pieces. Carina extending only t<> 

 base of the terga, the latter somet inn- 

 wanting. Scuta sub -oval. Tertiary 

 and Recent. 



Family 4. Verrucidae. Darwin. 



Shells sessile and composed of si.i 

 pieces. Of the scuta and terga on I it one 

 is free, the other plate in each being 

 fused with the rostrum or carina. 



The solitary genus Verruca, 

 Sclium., ranges from the Cretaceous to 

 Recent. 



Family 5. Balanidae. Darwin. 

 (Acorn Barnacles.) 



FlG - 1362 - 



PlO. 13.13. 



Lepas anatifirtt, Linn. 

 Recent ; Mediterranean C, 

 P, Peduncle; S, 

 T, Terguin. 



Carina ; 

 Scutun 



Shell obtusely conical, circular, or 

 oval in cross section, with broad calcar- 

 eous cellular base ; composed of four to (after Darwin). 

 ten lateralia, more or less completely 



fused at their sides, and two pairs of free terga and scuta which close the upper aperture 

 like an operculum. 



Of the lateral plates which comprise the crown-shaped immovable test, two are 

 designated as carina and rostrum, the pieces lying between and occurring in pairs being 



called lateralia. If additional plates are inserted 

 among the lateralia, they are termed according to their 

 position rostro- or carino -lateralia. The scuta and 

 terga lie free on the back of the animal, and in fossil 



FIG. 1364. 



Diagram of the shell of Ralanu*. B, 

 Basis; C, Carina; CL, Carino -lateral 

 compartment; L, Lateral compartment ; 

 R, Rostrum ; RL, Rostro-lateral com- 

 partment. Each valve or "comi>art- 

 inent " consists of a central " paries " (p) 

 flanked by " alae " (a) or " radii " (r). 



FIG. 1365. 



Scutum and terguin of llalnnus. A, External aspoct of t>r>:<iin, 

 showing "spur" below and "beak" above. B, Internal view ( 

 scutum, showing muscular scar (x). C, Internal view of tergum 

 (after Darwin). 



forms are generally lost. They have a very characteristic form, and hence are of 

 great systematic importance. Since among fossil species, however, only the marginal 

 plates are for the most part preserved, the determination of their structural characters 

 is often quite uncertain. 



Balanus, Lister (Figs. 1364-1367). Shell low, conical or cylindrical, composed of 



