1109 



CIRRIPEDIA. 



CIRRIPEDIA. 



1110 



This, the typical genus of the family, includes 39 receut species, 

 which ran!?e from 77 in the northern hemisphere to Cape Horn 

 in the south. 



Sub-genus, Acasta, Leach, 1817. Compartments six; parietea 

 and basis non-porose ; basia calcareous, cup-formed, not elongated : 

 attached to sponges or rarely to the bark of Isis. 



This sub-genus, which is a very natural one in habits and appear- 

 ance, nevertheless can hardly be distinguished from those species of 

 Balanua which live attached to Goryoitice. Acaita ia found in almost 

 all parts of the world. 



Tetraclita, Schumacher, 1817 (Coma of Leach, Astmui of Ranzani). 

 Compartments four, sometimes with their outer laminae calcined 

 together ; parietes permeated by pores, generally forming several 

 rows ; basis flat, irregular, calcareous or membranous. 



Tetraclita porota. 



Elminiui, Leach, 1825. Compartments four; parietes not poroae; 

 basis membranous. 



This genus is confined to the southern hemisphere. 



I'linjoma, Leach, 1817 (Megatrema of Leach; Adna of Leach; 

 Daracia of J. E. Gray ; Creutia of De Blamville ; Nobia of Sowerby). 

 Shell formed of a single piece ; basis cup-formed or sub-cylindrical : 

 attached to, or imbedded in corals. 



Pyrgoma crenatitm. 



a, specimens of the natural size in Astraa favosa ; 6, c, d, different views 

 and'aectiou of the cone ; , the opercular valves, b, c, d, and e, are magnified. 



Sub-genus Creuria, Leach, 1817. Compartments four ; furnished 

 with radii ; basis cup-formed, imbedded in corals. 



This aub-genus is most closely allied to Pyryoma, and its separation 

 is of doubtful propriety. 



Chelonobia, Leach, 1817 (Coromda of Lamarck ; Astrolepa* of Gray). 



Compartments extremely thick, six in number, but the roatrum 



is internally composed of three compartments united together ; basis 



membranous ; acuta narrow, united to the terga by a horny articular 

 ridge. 



Two of the three species included in this genus are always attached 

 to turtles ; the third adheres to crabs and smooth shells. 



Section ft. 



Scutum and tergum (when both are present) not overlapping each 

 other ; basis membranous ; parietes often deeply folded, with the 

 outer lamina towards the basis generally imperfect ; each branchia 

 composed of two plicated folds : shell attached to living Vertebrata. 



Coronula, Lamarck, 1802 (Diadema of Schumacher ; Cetopirus of 

 Ranzani). Compartments six, of equal breadth, deeply folded, with 

 the folds outwardly pressed together, but inwardly expanded, so as 

 to form cavities open only o'u the under side ; opercular valves much 

 smaller than the orifice of the shell : attached to C'etacea. 



Curonttla balcEtttirls. 



Platylepa,i. E. Gray, 1825 (Coronula of De Blainville). Compart- 

 ments six, each bilobed and inwardly produced, so as to form six 

 mid-ribs, which support the outwardly convex membranous basis. 



The speciea of this genus are attached to turtles, manatees, and 

 sea-snakea. 



Tubicinella, Lamarck, 1802 (Coronula of De Blainville). Compart- 

 ments six, of equal breadth ; shell sub-cylindrical, wider at the top 

 than at the basis ; belted by several transverse ridges : attached te 

 Cetacea. 



\ ^^^$^ 



N V "^ ^ --? 



'fuftif iiflfa trachealis. 



Xenobalanui, Steenstrup, 1852. Shell almost rudimentary, star- 

 formed, composed of six compartments, with a long peduncle-formed 

 body rising from the middle of them ; opercular valves none : 

 attached to Cetacea. 



Sub-Family. (,'hthamalince. 



Shell with the rostrum having also, but without radii ; rostro-lateral 

 compartments without alae on either side ; parietes not porose. 



Chthamalus, Ranzani, 1820 (Euraphia, Conrad). Compartments 

 six ; basis membranous, but sometimes in appearance calcareous from 

 the inflected parietea. 



C/ithamalui etellatus. 



