CALCAR. 89 



in the Synopsis of the British Museum, page 114, that the Bulliae 

 resemble the Nassse in most characters, u but they have a very 

 large, broad foot, and the hinder part of the inner lip of the shell 

 being extended beyond the mouth, forms a raised enamelled band 

 round the suture of the whorls, as is also the case with the Ancil- 

 lariae and some Volutes." Bullia vittata, fig. 427, is an example 

 of the genus. The name Subula is given by De Blainville to the 

 other species of Terebra, so that if both these genera were ad- 

 mitted, the old genus Terebra must be expunged. 



BULLINULA. Beck. Species of Bulla, with produced conical 

 spires, fig. 253. 



BYSSOARCA. Sw. (Byssus and Area.) Fam. Arcacea, Lam. A 

 genus of bivalve shells, composed of the Area Now, and several 

 other species, separated from the genus Area on account of their 

 shells being attached by means of a byssus passing through an 

 hiatus in the ventral margins. B. Now, fig. 132. The species 

 occur in Southern Europe, East and West Indies, China; also, 

 on the coasts of Great Britain. 



BYSSOMYA. Cuvier. ( Byssus and Mya.) De Blainville states that 

 although the shell of this proposed genus resembles Saxicava, 

 the animal is sufficiently different to justify the separation. 



BYSSUS. (Bvavog, byssus, ancient name for linen.) The ten- 

 dinous fibres by which some Bivalves are as it were anchored or 

 moored to sub -marine substances. A fine example of this is to 

 be seen in the Pinnse which bear some resemblance to large 

 Muscle Shells and have an hiatus in the margins of the valves 

 through which a bunch of silken fibres passes. In the British 

 Museum there is preserved a pair of gloves which have been 

 woven of these fibres. The Byssus is peculiar to some bivalve 

 shells such as Muscles, Hammer Oysters, Area Nose, &c. 



CALCAR. Montf. (a spur.) A genus composed of Trochus 

 stellaris, Lam. and other depressed species of Trochus which 

 are characterized by a stellated keel round the angle of the last 

 whorl ; but not including T. Imperialis, which is the genus Impe- 

 rator, Montf. The difference consists in the latter being umbili- 

 cated and the former not. T. stellaris, fig. 358. 



