MONTACUTA. 71 



MONTACUTA. Turton. 



Shell small, thin, equivalve, inequilateral, transversely 

 oblong, or obliquely oval, surface smooth, or concentrically 

 striated, or rarely radiatingly furrowed. Beaks inflected. 

 Inner margins smooth. Hinge-margin with a trigonal in- 

 cision, and cartilage pit, and a pair of diverging laminar 

 teeth in one or both valves. Ligament internal. Mus- 

 cular scars suborbicular, pallia! impression simple. 



Animal oblong, its mantle freely open in front, with sim- 

 ple margins, not furnished with siphonal tubes posteriorly ; 

 a single siphonal orifice (anal) or none (?). Foot very 

 large, strong, and broad, furnished with a byssal groove. 



The composition of this genus is still unsatisfactory, and 

 it is very possible that when the animals of the several 

 species shall be better known, a division of the group will 

 become necessary. Montacuta substriata is possibly the 

 type of a distinct genus, but in the present state of our 

 knowledge we prefer keeping the species known as Monta- 

 cuta together, with the exception of M. purpurea. Re- 

 cluz has united them with the Kelli<e, to which, indeed, 

 they are very nearly allied. They are all minute and in- 

 conspicuous bivalves, possessed of considerable powers of 

 locomotion, yet also in the habit of mooring themselves 

 firmly by means of a byssus. Their generic appellation 

 was given in honour of Montagu, a name deeply reverenced 

 by every British malacologist and deserving of some more 

 conspicuous testimonial. 



The genus dates its genealogy from the epoch of the 

 coralline crag in which our M. substriata and another 

 species have been found fossil. 



