ADDENDA. 109 
Geological Positions and Localities. his oyster appears to be abundant in the Upper 
Bathonian Clays of Wiltshire. Mr. Walton has collected it in the Forest Marble of Pound 
Pill, Farleigh, and Hinton, also in the Cornbrash of Hilperton. 
Genus— Harpar—Parkinson, 1811. Deslongchamps, 1858. 
Shell irregular, inequivalve, attached by the umbo of the larger or right valve ; surface 
radiately ribbed or smooth, usually with concentric, irregular, lamellose plications, imbricated 
or tuberculated ; borders of the valves close fitting and irregular. . 
Hinge in the attached valve consisting of a large, flattened, triangular plate, traversed 
by a central perpendicular or oblique furrow to receive the ligament, with somewhat 
elevated borders, exterior to which are slightly marked diverging sulcations to receive the 
elevated borders of the ligamental groove in the other valve; the outer borders of the 
plate form lengthened and elevated dental processes. 
Hinge in the left or free valve with a triangular plate traversed mesially by the liga- 
mental groove, the borders to which are elevated and but slightly diverging ; exterior to 
these are strongly impressed grooves to receive the dental processes of the other valve ; 
the dental processes forming the diverging borders of the plate are but little produced. 
The hinge plate in each valve has transverse striations of growth. 
The adductor scar is round, placed posterior to the middle of the valve, and strongly 
marked ; the pallial sinus is simple. 
The genus Harpax having originally been imperfectly described by Parkinson, and 
founded upon a single small species, remained but little noticed and accepted by few 
authors until the year 1858, when it was re-established and amply illustrated in a copious 
work* on the ‘ Fossil Plicatulas and allied Genera,’ by that eminent and veteran paleeon- 
tologist M. Eudes, E. Deslongchamps, who to the long list of memoirs in which he has so 
ably developed and illustrated the Jurassic fossils of Normandy, has added the present, 
which probably surpasses all the former in the critical acumen and lengthened researches 
which it has necessitated. Of the fifteen species of Harpax known to M. Deslongchamps 
all are Liassic, with one exception (//. scapha), from the ferrugmous (Inferior ?) Oolite of 
Longwy ; the following fine species is therefore the first example of the genus in the 
oolites of this country. 
* Essai sur les Plicatules fossiles et quelque autre genres voisins ou démembrés de ces coquilles, 
par M. J. A. Eudes Deslongchamps. Extract du Xle volume des ‘ Memoires de la Société Linnéenne de 
Normandie,’ Caen, 1858. 
