SUPER-ORDER IV CIRRIPEDIA 651 
Lepas, Linn. (Fig. 1363). Peduncle naked. Capitulum consisting of only two 
very large triangular scuta, two small terga, and a single carina. Pliocene and Recent. 
Poecilasma, Darwin.  Capitulum 
consisting of three, five, or seven 
pieces. Carina extending only to 
base of the terga, the latter sometimes 
wanting. Scuta sub-oval. Tertiary 
and Recent. 

Family 4. Verrucidae. Darwin. 
EE Aaa all wht may 
Shells sessile and composed of six 
pieces. Of the scuta and terga only one 
is free, the other plate in each being 
fused with the rostrum or carina. 
The solitary genus Verruca, 
Schum., ranges from the Cretaceous to 
Recent. 


CA mr oe 
LOT. 





"LL 
LL 
Family 5. Balanidae. Darwin. y 
(Acorn Barnacles.) 1 
Fic. 1363. 

Shell obtusely conical, circular, or Fic. 1362. Lepas anatifera, Linn. 
oval in cross section, with broad calcar- Scalpellum fossulum, Dar- Recent ; Mediterranean C, 
? win. Carina much enlarged Carina; P, Pedunele; S, 
cous cellular base 5 composed of four to (after Darwin). Scutum ; 7’, Tergum. 
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 compose 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 

b 

Fic. 1364. 
Diagrain of the shell of Balanus. B, 
Basis; C, Carina; CL, Carino-lateral Fic. 1365 
compartinent; L, Lateral compartment ; Hes Bae 
R, Rostrum; RL, Rostro-lateral com- Scutum and tergum of Balanus. A, External aspect of tergum, 
showing ‘‘spur” below and ‘‘ beak” above. 3B, Internal view of 
partment. Each valve or ‘‘compart- 
ment” consists of a central ‘‘ paries ” (p) scutum, showing muscular scar (2). 
flanked by ‘‘alae” (a) or “‘ radii” (7). (after Darwin). 
C, Internal view of tergum 
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. 1864-1367). Shell low, conical or cylindrical, composed of 
