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 Hasis, proposed by Schumacher, the species which possess 
a lateral tooth or lamina, and reserving to So/en 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 Paleozoic 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. Mason. WNyst. Coq. Foss. de Belg., p. 44, pl. 1, fig. 3, a, 6, 1844. 
Ensis compLanatus. J. Sowerby. Min. Conch., t. 642, figs. 2, 4. 
Spec. Char. Testi elongata, recta, levigatd ; extremitate anticd obtuse truncatd ; in 
valvd sinistrd unidentato, in alterd bidentato ; dentibus lateralibus elongatis, marginatis. 
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, 1 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, pl. 312, fig. 4, the 
Solen is depicted with the siphons at the anterior side; and in pl. I of the ‘ Hist. of Brit. Moll.,’ all the 
animals are there represented as having the foo¢ on the posterior or ligamental side of the shell. This is 
evidently the result of haste, or of the too numerous ayocations 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. 
