CLASSIFICATION OP THE BUACHIOPODA. 121 



Shell of a triangular shape, with very unequal valves ; larger valve sub-pyramidal ; 

 beak acute, bent backwards ; hinge line straight ; area large, triangular, slightly curved, 

 and divided by a long narrow mesial elevation, extending from the apex to the cardinal 

 edge, and longitudinally depressed along its centre ; smaller valve semicircular, operculi- 

 form, slightly convex or almost flat, with a narrow sub-parallel triangular area. Exterior 

 smooth, or encircled by concentric lines of growth, passing uninterruptedly over the area ; 

 hinge line crenulated. The cavity for the animal is small in proportion to the dimensions 

 of the shell. The interior of the smaller valve is divided by a slightly elevated mesial ridge 

 or septum, terminating at the hinge line in a small cardinal process, which is hollowed in 

 the middle ; from the whole extent of the hinge line a number of punctate striae radiate to 

 the margin ; on each side, close to the hinge-line, in the vicinity of the cardinal angles, 

 is a series of short parallel unequal elevated ridges. In the interior of the larger valve a 

 corresponding series of punctate striae proceeds from the whole margin, and converge 

 towards the bottom or cavity of the shell, but becoming more elevated and produced at the 

 cardinal edge, where they form unequal asperities ; in the centre, and near the hinge line, 

 a larger rounded projection (corresponding to the first described in the other valve) extends 

 to the bottom of the shell, in the shape of a narrow mesial depression. 



Ohs. Of all the genera among the Brachiopoda, Calceola seems the most abnormal ; 

 no one has been able to point out the probable structure of the animal, nor has its true 

 position in the class been yet satisfactorily ascertained. One would have imagined that 

 such a ponderous shell would have been provided with a powerful muscular system, still 

 no traces of it have been observed in the interior of the valves ; and so great was the 

 amount of calcareous matter deposited internally, that in many examples hardly any free 

 space remained to lodge the animal. Some authors have expressed doubts whether this 

 genus should be ranked among the Brachiopoda ; Cuvier, in his ' Regne Animal,' classes it 

 with the Oysters ; Lamarck, and a few other Conchologists, place it in the family of 

 Riidistes, whence it was removed by M. Deshayes and Goldfuss ; it is now generally 

 admitted to belong to the Palliobranchiata. The type of the genus, Calceola sandalina, 

 has been long known under various appellations.^ 



Its Geol. range is confined to the Devonian period. Only one well-authenticated 

 species has been discovered." 



Example: C. sandalina, Linn., Gmel., sp. 



' Hiipsch described and figured it in 1768, and Beuth, in 1776. Goldfuss has likewise published 

 excellent illustrations of the species, in his 'Petrefacten Musei Universalis,' pi. clxi. 



2 M. de Koninck has lately stated in the seventh volume of the 'Ann. des Sciences Royales of Liege,' 

 that the so-called Calceola Dumontiana does not possess the characters of that genus, and even doubts 

 whether the species belongs to the class ; he terms it Hypodema. 



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