CRUSTACEA. 637 



A slit-like orifice between the opercular valves leads into the 

 sac in which the body is lodged. The valves are two on each side, 

 tergum and scutum. The tergum has three margins, the scutal, basal, 

 and carinal / on the basal margin a spur (calcar) depends. The 

 scutum has also three margins, the basal, tergal, and occludent, so 

 called from opening and shutting against the opposite valve. DARWIN 

 Balanidce, pp. 37.] 



Coronula BLAINV. Operculum not articulated together, com- 

 posed of two or four calcareous pieces united by membrane. 



Coronula LAM., Diadema RANZANI. Shell depressed, conical or 

 suborbicular, with very thick walls excavated internally by radiating 

 cells. 



Sp. Coronula diadema L., BLAINV. Malacol. PI. 86, fig. 4, Cuv. R. Ani. d. 

 ill., Mollusq. PI. 139, fig. 2, on the Fin-fish, Balcencenoptera, Balcena 

 longimana. 



Tubicinella LAM. Shell tubular or cylindrical, belted by trans- 

 verse ribs or rings. Operculum with four valves. 



Sp. Tubicinella balcenarum LAM. Ann. du Mus. I. Tab. 30, fig. I, BLAINV. 

 Malacol. Tab. 86, fig. 5, GUERIN Iconogr., Mollusq. PL 38, fig. 14 ; lives 

 parasitically in the skin of the whale of the southern hemisphere (Balcena 

 Mysticetus antarctica) . 



Balanus BRUG. (exclusive of some species), LAM. Shell conical, 

 composed of six laminae or valves. Operculum articulated, subver- 

 tical, consisting of four valves. 



Sp. Balanus sulcatus LAM., Lepas balanus L., BASTER Natuurk. Uitsp. i. 

 Tab. xn. figs. 7 10 ; Balanus miser LAM., Encycl. mifh. Vers. PI. 64, 

 fig. 4, &c. 



Acasta LEACH. 

 Creusia LEACH. 

 Pyrgoma SAVIGNY. 



Note. On this and some other genera, proposed by RANZANi 1 and 

 others, compare MILNE EDWARDS in the new edition of LAMARCK'S Hist, 

 not. des Anim. s. Vertebres, v. 1838, pp. 669672. 



1 Observationi su i Balani ; Opuscoli scicntifice di Bologna I. 1817, pp. 195 202, 

 pp. 269 276, ii. 1818, pp. 63 93. 



