MALENTOZOA. SESSILIA. 351 



angular, striate, rather acute, induplicate at the end, and with 

 a deep groove on their articular margin ; the colour white, 

 sometimes tinged with yellow or pink ; the hase a thin cal- 

 careous plate, divergingly striate, and with some faint con- 

 centric lines. 



It varies considerably in form, being variously distorted by 

 being crowded, sometimes elongated and claviform, often irre- 

 gularly rugose, but not ridged. It adheres very firmly, so as 

 to be with some difficulty detached, and is strong, so as not to 

 be capable of being crushed by the fingers. The elongated 

 forms may be distinguished from those of Balanus elongatus 

 by the smoothness of the valves, and the different form of the 

 operculum, as well as by the calcareous bases. 



It adheres to mussels, limpets, crabs, and shells of various 

 other animals, as well as rocks, and piles ; and is very com- 

 mon on many parts of our coasts, as well as in deep water. 



As Balanus balanoides is tautological, Lamarck's name 

 seems preferable. 



Lepas balanoides. Linn. Syst. Nat. 1108. — Lepas balanoides. 

 Peun. Brit. Zool. iv. 72. PI. 37. f. 5. — Lepas coruubiensis. Pemi. 

 Brit. Zool. iv. 73. PI. 37. f. fi — Balanus balanoides. Mont. Test. 

 Brit. 7.— Balanus ovularis. I>anik. Syst. v. 392; Ed. 2. v. 6G0.— 

 Balanus ovularis. Brown, Illustr. PI. G. f. 4. PL 7. f. 17. 



2. Balanus Cormihiensis. Divarf Acorn-Shell. 



Shell conical, truncate, with the six valves distinctly sepa- 

 rated by a narrow groove, which is not wider at the upper 

 part ; the ventral valve largest, the ventro-lateral nearly equal, 

 the dorso-lateral small, the dorsal rather large ; all more or 

 less longitudinally rugose, often transversely wrinkled, the 

 rugae rib-like at the base, and the surface roughish or punc- 

 tured ; ventral opercular valves triangular, transversely ru- 

 gose, rather acute, with their marginal outline somewhat con- 

 vex ; dorsal opercular valves triangularly striate, with their 

 marginal outline convex, tlie tips incurved and rather obtuse, 

 and a sinus on the articular margin, receiving a convex pro- 

 cess of the other valves ; the colour white, greyish, or brown- 

 ish, the base membranous. 



Easily distinguishable from Balanus balanoides by its rugo- 

 sity, diminutive size, the convexity of the opercidum, and its 

 mode of articulation, yet nearly allied to it, this species varies 

 considerably in form, being sometimes nearly cylindrical, but 

 never shooting up to any great height. Its base being mem- 

 branous, it is easily detached, altliough the shell is rather 

 2 H 



