MUREX. 193 



is interrupted to leave a space for the head; while in Siphonaria 

 it is nearly half way between the anterior and posterior ends of 

 the shell. 



MOUTH. The aperture or opening of univalve shells. 



MULINIA. Gray. A genus composed of species of Mactra, 

 Auct. described as having the ligament (properly so called) inter- 

 nal, and lateral teeth simple. Ex. fig. 82. M. bicolor ; Mactra, 

 Auct. 



MULLERIA. Fer. Fam. Ostracea, Lam.— Descr. Irregular, sub- 

 quadrate, inequivalve, inequilateral, foliaceous, attached, pearly 

 within, green, horny without ; hinge irregular, with a partly 

 external ligament, passing to the interior, through a sort of sinus. 

 — Obs. This remarkable shell resembles Etheria in general form 

 and appearance, but is distinguished by having only one muscular 

 impression. It is so rare that, although not very beautiful, a 

 specimen has been known to produce £20. at a sale. Fig. 192. 



MULTILOCULAR. Many chambered. 



MULTISPIRAL. (Multus, many, spira, spire.) A term applied to 

 a shell when the spire consists of numerous whorls ; or to an 

 operculum of numerous volutions. 



MULTIVALVE. (Multus, many ; valva, valve.) Consisting of 

 numerous valves. There are three kinds of multivalve shells : 

 1st. Those in which the valves are arranged in pairs, and produce 

 a flattened figure, as Pedunculated Cirripedes, fig. 34 to 43 ; 

 2nd. Those in which they are arranged circularly, as Sessile 

 Cirripedes, the valves of which are of two kinds ; the opercular, 

 consisting of several valves, which close the aperture, and the 

 parietal, consisting of those which surround the body of the 

 animal in a circular form, fig. 14 to 33. 3rd. Those in which 

 they are arranged in a straight line, as Chiton, fig. 227. 



MUREX. Auct. (A sharp rock.) Fam. Canalifera, Lam. sipho- 

 nostoma, Bl. — Descr. Turrited, ventricose, thick, with three or 

 more longitudinal, continuous, branched, spinose or fringed 

 varices ; spire prominent, acute ; aperture oval, terminating in 

 a posterior, partly closed canal, outer lip varicose, inner lip 



6 



