3* 



NOMENCLATURE OF THE SHELL OF A SESSILE CIRRIPEDE. 



SHELL. Fig. 1. 



Orifice of shell, surrounded by the sheath. Sheath formed by the alee (a — a.) and by portions of the 

 upper and inner surfaces of the parietes (p—p.) 



p. p. Parietes 



Basis 



r. r. Radii 

 a. a. Alae 



t^k Basis 



n.b. In Balanus, and many other genera, the Rostrum and Rostro-lateral compartments are confluent,. 



and hence the Rostrum has the structure of Fig. 2 



Fig. 2. 



COMPARTMENTS. 



Fig. 3. 



Fig. 2. Compartment with two radii, serving either as a Rostrum or Rostro-lateral compartment. 

 Fie 3. serves as a Lateral and Carino-lateral Compartment. Fig. 4. serves as a Carina or Rostrum. 



OPERCULAR VALVES. 



Fig. 6. Tergum (external view). 



Fig. 5. Scutum (internal view of). 



Occludknt Margin 



Cavity for Adductor ■—/ 

 "Muscle. 



Adductor Rid-^e 



y Tergal Margin 



y- Articular Ridge 

 r Articular Furrow 



— Cavity for the Lat. 

 Depressor Muscle 



Beaked 

 Apex 



Scutal :' 



Margin 



Basal Margin 



i 



Spur 



Carina i. 

 Margin- 



Basal 

 Margin 



Fig. 7* Tergum (internal view). 



Carinal Margin 



Apex 



Articular Ridge 

 Articular Furrow 



Scutal Margin 



Crests for Depressor 

 Muscle 



Basal Margin 

 Spur 



