9 



LEPT/ENA, Dalman. 



Objections have been so strongly urged against the name 

 Productus, that vve have found it necessary to adopt Dal- 

 man's name Leptaena for this genus. It is characterized 

 by the hinge-area in each valve extending the whole width 

 of the shell, and by the margins of the valves being pro- 

 duced together beyond that part of the shell vvhich contains 

 the animal, and bent down so as to form a kind of inverted 

 cup. The flatter (lower) valve has no projecting beak, 

 but in the middle of its hinge-line is a process which nearly 

 fits the aperture in the convex deltidium of the other valve, 

 which slides upon it as it opens or closes; this process 

 is divided within into two diverging teeth. The same 

 valve has a smaller longitudinal septum in its middle, be- 

 tween the muscular impressions. The beak of the (upper) 

 convex valve is in some species produced considerably. 

 All the species have striated surfaces, and many have long 

 spines, often tubular, on the outside, and numerous little 

 spine-like projections within. 



LEPTtENA anomala. 

 TAB. DCX\\—fg. 1. 



Spec. Char. Irregularly triangular, elongated, com- 

 pressed, striated ; beak very much produced, its 

 sides spinose ; hinge-area large, triangular. 



Syn. Pinna inflata. Phillips, Geol. Forks. Part 11 

 211. PL VI. f. I. Mytilus striatus. Fischer, 

 Orycht. Mosc. 181. PL XIX. f. 4. 



A VERY irregular and often distorted shell, with a surface 

 and texture precisely similar to that of Leptcuna scnbricula 

 and the other species of the genus. 



Individuals rarely occur separate : they are commonly 

 distorted, broken, and imbedded one in another, which 

 renders them very difficult to comprehend. The spines 

 near the hinge are small, they are best defined in fig. a.; 

 their bases are seen on the internal cast (fig. d.). Fio-s. 

 bb. are two views of one specimen, which shows the large 

 area beneath the beak, an approach to which is seen at fig. 

 3 b. Those found in Russia are often much larger and 

 less elongated, therefore more resembling the ordinarv 

 form of Leptaena. The specimen represented at fig. 1 c, is 

 in Mr. Gilbertson's cabinet ; it is from the mountain lin)e- 

 stone of Holland. I am not acquainted with the localities 

 of the others. 



Vol. VII. c 



