140 THE CRUSTACEA 



SUB-CLASS CIRRIPEDIA. 



ORDER l. Thoracica. 

 A mantle present. Six pairs of cirriform trunk-appendages. 



SUB-ORDER 1. Pedunculata. 



Peduncle and capitulum distinct. Outer plates of shell, when present, 

 not forming a "wall." 



Family LEPADIDAE. Lepas, Linn. (Fig. 57, A) ; Dichelaspis, Darwin ; 

 Pollicipes, Leach (Fig. 60); Scalpellum, Leach (Fig. 61); Ibla, Leach (Fig. 

 71) ; Lithotrya, Sowerby ; Conchoderma, Olfers ; Alepas, Rang ; Anelasma, 

 Darwin (Fig. 68) ; Koleolepas, Stebbing. 



SUB-ORDER 2. Operculata. 



No peduncle. Scuta and terga forming a movable operculum. Outer 

 plates of shell coalesced to form a " wall." 



TRIBE 1. ASTMMETRICA. 



Scutum and tergum of one side movable, without depressor muscles. 

 Family VERRUCIDAE. Verruca, Schum. 



TRIBE 2. SYMMETRICA. 



Scuta and terga of both sides movable, with depressor muscles. 



Family BALANIDAE. Balanus, Lister (Fig. 57, B) ; Coronula, 

 Lamarck ; Tubicinella, Lamarck ; Xenobalanus ) Steenstrup (Fig. 65) ; 

 Elminius, Leach ; Pyrogoma, Leach. Family CHTHAMALIDAE. Chtha- 

 malus, Ranzani ; Catophragmus, Sowerby (Fig. 62) -- Octomeris, Sowerby. 



ORDER 2. Acrothoracica. 



A mantle present. Trunk -appendages reduced in number, the 

 posterior pairs widely separated from the first pair. 



Family ALCIPPIDAE. Alcippe, Hancock (Trypetesa, Norman) (Fig. 72). 

 Family KOCHLORINIDAE. Kochlorine, Noll. Family CRTPTOPHIALIDAE. 

 Cryptophialus, Darwin. 



ORDER 3. Ascothoracica. 



Mantle containing diverticula of alimentary canal. Trunk-append- 

 ages more or. less reduced. 



Family LAURIDAE. Laura, Lacaze-Duthiers (Fig. 76). Family 

 SYNAGOGIDAE. Synagoga, Norman. Family PETRARCIDAE. Petrarca, 

 Fowler. Family DENDROGASTRIDAE. Dendrogaster, Knipowitsch (Fig. 

 78). 



ORDER 4. Apoda. 



Mantle absent. No trunk-appendages. 



Family PROTEOLEPADIDAE. Proteolepas, Darwin (Fig. 79). 



