250 NEW-YORK FAUNA — MOLLUSCA. 



ORDER V. CIRRHOPODA. 



Animal enveloped with a mantle in the form of a sac, which is open only behind, enlarged 

 at the inferior portion, terminated above by a certain number of pairs of cirri, which are 

 long, corneous, articulated, ciliated and curving at the summit. Head not distinct, with- 

 out eyes or tentacles ; mouth with lateral corneous dentated and articulated jaws. Gills 

 in pairs on each side at the base of the first cirri ; anus central at the base of this tube. 

 Shell very variable in form, and composed (except in one genus) of many valves, ad- 

 herent either directly or indirectly by means af a fleshy tube. Marine. 



FAMILY BALANID&. 



Animal resembling those of the Lepadae, but without peduncle, and with its branchice in the 

 form of two fringed wings attached to the internal surface of the mantle. Marine. Shell 

 solid, conical or cylindrical, formed of one or more pieces united laterally, open at the base, 

 or closed by a membranous or calcareous partition by which it adheres ; always open above, 

 but furnished there with a pyramidal opercle consisting of two or four valves. 



Obs. About ten generic groups have been described. 



GENUS CORONULA. Lamarck. 



Animal with the characteristics of the family. Shell depressed, formed of six triangular 

 pieces, conoid, truncated at its extremity ; walls very thick, with radiating cells. Opercle 

 of four small triangular valves, joined to the opening of the tube by a membrane. 



CORONULA DIADEMA, 



Lepas diadema, Lin. C. id. Gould, Invertebrata of Mass. p. 12. 



Description. Shell globose-conical, truncated at the tip. Surface with twelve triangular 

 compartments : six with the tips downwards, plain and transversely striated ; six with the 

 tips upwards, and with four rounded ribs marked across with beaded folds. Orifice mostly 

 closed by a membrane, through a fissure in which, closed by two valves, the arms are pro- 

 truded. 



Height, 1-0. Diameter, 1-5-2-0. 



