90 



CRUSTACEA CIRRIPEDIA 



iis the hard sharp objects which cover rocks and piles near liigh- 

 water mark on every sea-coast. If we examine the hard skeleton 

 of one of these animals, we find that, unlike the Pedunculata, they 

 possess no stalk, the capitulum being fused on to the surface of 

 attachment by a broad basal disc. Typically, there may be 

 considered to be eight skeletal pieces forming the outer ring which 

 invests the soft parts of the animal, an unpaired rostrum and 



carina, and laterally a 

 pair of rostro - lateral, 

 lateral, and cariuo-lateral 

 "compartments," as shown 

 in Figs. 60, 63. 



The skeletal ring is 

 roofed over by a pair of 

 terga at the carinal end 

 and a pair of scuta at 

 the rostral end ; these 

 four plates make up the 

 operculum hj which the 

 animal can shut itself 



Fig. Q\.~BahmustinUnnahaum, with the right half Completely up in its shell, 



of tlie shell and of the operculum removed, .seen or between the valvCS of 



from the right side. A, Antennae, the size of i • i •. i. ^ • i. 



which is exaggerated ; A.M, adductor muscle : whlCh it Can protrude itS 



B, basis ; C, carina ; Cr, cirri or thoracic appen- li^^bg for obtaining food. 



dages ; I), oviduct ; G, ovary ; Z, lateral com- . c ^ 



]>artment ; Lb, labrum or upper-lip ; M, If, The relation 01 the 



depressor muscles of scutum and tergum ; il/.C, animal to itS shell is 

 mantle-cavity ; O, orifice of excretory organ ; 



O.M, opercular membrane; Jt, ro-stnim ; S, showil ill Fig. 61. The 



Sne"Dar5;i.r^'°" "' '*°™'''' ' ^ '''°"'"' ^^^'^^^ ''' ^he Operculata is 



not merely secreted as a 

 dead structure on the external surface of the epidermis, but repre- 



FiG. 62. — Diagrammatic section 

 of the growing shell of Bal- 

 antis jiorcatns. C, Canals ; 

 Ct, cuticle ; H, hypodermis 

 (= epidermis) ; //', part of 

 shell secreted by the hypo- 

 dermis ; HI, hypodermal 

 lamina ; J/, part of shell 

 .secreted bv the mantle. 

 (After (Jfuv'el.) 



sents a living calciferoiis tissue interpenetrated by living laminae 



