254 MOLLUSCA FROM THE CRAG. 



Animal narrow, and more or less cylindrical, with the mantle united at the borders, 

 except in front, where it is open for the passage of a large and truncated foot. Siphons 

 short and united, their margins fimbriated. 



The generic character is here intended for the reception of those species known 

 under the familiar appellation of Razor Shells, of a form resembling the handle of our 

 common razors. A few modern authors still consider that the differences possessed 

 by some of the shells of this peculiar form entitle them to a further division, and have 

 united, under the name of Ensis, proposed by Schumacher, the species which possess 

 a lateral tooth or lamina, and reserving to Solen those only in which this linear or 

 transverse appendage is wanting. 



The hinge of this genus is more anterior than that of any of the Bivalves, being 

 situated at the extremity of the shell. Probably a more than usual strength of union 

 for the two valves was required at this part to resist the action of its large and 

 powerful foot, in consequence of the burrowing habits of the animal.* 



This appears a modern genus, no true species having as yet been described as 

 belonging to any Formation more ancient than the Lower Tertiaries, where some of 

 the species deviate slightly from the type, the hinge not being quite at the extremity. 

 The few shells somewhat of this form, found in the Palaeozoic Rocks, are very 

 doubtful Solens. 



1. SOLEN GLADIOLUS, Gray. Tab, XXV, fig. 8, a c. 



SOLEN GLADIOLUS. Gray. Zool. of Beechey's Voy., p. 153, t. 43, figs. 4, 4, 1839. 



ENSIS var. MAJOR. Nyst. Coq. Foss. de Belg., p. 44, pi. 1, fig. 3, a, b, 1844. 

 ENSIS COMPLANATUS. J. Sowerby. Min. Conch., t. 642, figs. 2, 4. 



Spec. Char. Testa elongatd, recta, Icevigatd ; extremitate anticd obtuse truncatd j in 

 valvd sinistrd unidenlalo, in alterd bidentato ; dentibus lateralibus elongatis, marginalia. 



Shell lineal or subcylindrical, straight and smooth, anterior extremity obtusely 

 truncated ; one cardinal tooth in the left valve, and two in the other ; lateral teeth 

 marginal. 



Length, 5 inches. Height, \ inch. 



Locality. Red Crag, Walton Naze and Suffolk. 



Recent, Arctic Seas. 



* Some confusion has existed respecting the anterior and posterior sides of these shells. Poli has 

 given a good and correct representation of one of the species of this genus, with its foot protruded at the 

 anterior, and the siphons at the opposite extremity. In the 'Ency. Method.,' vol. iii, pi. 312, fig. 4, the 

 Solen is depicted with the siphons at the anterior side ; and in pi. I of the ' Hist, of Brit. Moll.,' all the 

 animals are there represented as having the foot on the posterior or ligamental side of the shell. This is 

 evidently the result of haste, or of the too numerous avocations of the late much lamented and talented 

 author of the Malacological portion of that beautiful work, preventing the bestowal of a necessary attention 

 for the avoidance of these trifling errors. 



