96 TURTONIAD.E. 



then by the retractor muscle it is drawn forward, making such 

 rapid progression as to cross a watch-glass in a minute, and on 

 the passage turns itself several times by a twist of the foot 

 from side to side. No siphonal processes, nor even a simple 

 orifice, were observed. When opened, the large foot is the 

 most prominent object ; with a good lens the byssal fissure is 

 distinctly visible. Though there are traces of a branchial 

 lamina, we could not detect its configuration, nor the presence 

 of palpi. In the hinge, under the beaks, there is a minute 

 obsolete primary tooth or two, with only a single compressed 

 triangular lateral, in both valves, but on the longer side only, 

 which is the anterior one. This structure differs much from 

 Kellia. 



Some malacologists call what we term the lateral teeth in 

 Kellia and this genus, the cardinal ones ; but as in them there 

 is no moveable ossicle, we consider the minute denticles at the 

 edge of the cartilage-pit, directly under the beaks, the primary 

 ones. But the case is different in those minute species styled 

 by authors Montacuta bidentata and M. ferruginosa', these 

 have been removed by us to the Anaim, as they have the 

 characteristic ossicle of the family ; in them there are no 

 minute cardinal teeth, and what in Kellia and Montacuta are 

 termed laterals, here become of cardinal value. 



TURTONIAD.E, Clark. 



We have been obliged to establish this family for Turtonia, 

 with a single genus of only one species, planted by authors in 

 the Kelliadce, though it has not the slightest community of 

 attributes or structure with any of the genera of that group. 

 Lepton, Galeomma, Kellia and Montacuta are as far asunder 

 from it as the poles. We mention a convincing proof of its 

 heterogeneity : in all the species of those genera, excepting 

 perhaps Kellia suborbicularis, in which the sides are nearly 

 equal, the shortest is the posterior one; but in Turtonia 

 minuta the longest is posterior, and it is the only animal of 

 these tribes that has a considerably produced anal siphon. 



