MUSCULAR AND ALLIED SYSTEMS. 93 



end to the ventral valve. The fibres of the posterior 

 occlusors (indicated by black paper inserted beneath them), 

 unlike those of all the other muscles, are transversely 

 striated. The striped muscle probably first suddenly closes 

 the valves, the closed state being maintained by the un- 

 striped anterior occlusors. The divaricators rise from the 

 ventral valve alongside the insertion of the occlusors, and 

 are inserted upon the cardinal processes of the dorsal valve 

 external to the hinge-fulcrum. The peduncular muscles 

 give rise to the slight movements of the valves upon the 

 stalk ; there are two pairs passing to either valve from 

 the sides of the peduncle. 



Presented by Prof. G. B. Howes. 

 Hancock, Phil. Trans., vol. cxlviii. 1858, p. 795. 



C. 21. A Cirripede (Lepas anatifera) dissected from the right side 

 to show the muscular system. The most important muscles 

 are : An adductor, passing transversely between the scuta, 

 for the closure of the valves ; a group of longitudinal 

 muscles on the carinal body-wall, apparently to retract the 

 animal into its shell ; a series of muscles passing transversly 

 from side to side in the position of the decapod sternum ; 

 and the various muscles of the appendages. The majority 

 of the muscle-fibres are transversely striated, but smooth 

 fibres occur in the adductor muscle, mantle and peduncle. 

 O.C. 54 A. 



C. Darwin, Monograph of the Cirripedia, Bay Soc. 1851, 

 p. 39 ; Gruvel, C. R. Acad. Sci., t. cxxiii. 1896, p. 68. 



C. 22. The stem of the Eared Barnacle (Conchoderma aurita), 

 deprived of its external theca to show two series of oblique 

 muscular fibres which arise from a central line or tendon 

 on one side of the stem, and, winding spirally round, are 

 inserted into a similar line on the opposite side of the stem. 

 Beneath these oblique fibres, whose office is to compress 

 the peduncle, others may be observed which are longi- 

 tudinal, for the purpose of shortening the peduncle. 

 0. 0. 62, Hmiteriaji. 



