THE BRITISH FOSSIL BRACHIOPODA. 377 



What are the genera that should constitute the families Orthisida and 

 cannot yet be finally determined. It is a large subject and demands further consideration 

 and investigation. The species belonging to those two families are likewise very numerous. 



In the Orthisidce it will certainly be necessary to include such genera as Orthis, 

 Enteletes, Schizophoria, and Skenidium. King would also place in the family his two 

 genera Platystrophia and Liccelosia, but which for the present I feel disposed to leave 

 with Orthis. 



The genus Orthis was proposed by Dalman in 1828 with the following diagnosis : — 

 " Testa inaequivalvis, aequilatera ; valva minori subplana, majori convexa. Margo cardi- 

 nalis rectilineus, latus, foramine deltoideo sub nate valvas majoris." In this genus he 

 places nine species, viz. Orthis ? pecten, 0. striatella, 0. zonata, 0. callactis, 0. colli- 

 gramma, 0. testudinaria, 0. basalis^ 0. elegantula, and 0. demisa, but we must exclude 

 from it the first, as he places a point of interrogation after the name Orthis. The second 

 also must be excluded, for it belongs to the genus Chonetes. We would therefore take 

 his Orthis elegantula or 0. calligramma as the type of the genus Orthis, and this would 

 agree with his diagnosis. 



The name Enteletes was mentioned for the first time by Fischer de Waldheim in 1825, 

 but he did not then describe his genus or refer to any species ; and it was only in 1837 

 that he described his Enteletes in the ' Oryctographie du Gouvemement de Moscou,' p. 

 141. Fischer seems not to have understood or to have made up his mind with 

 reference to the type of his genus. In 1809 he figured the type under the name of 

 Terebratula octoplicata. In 1825 he gave to the same fossil the name of Choristites 

 LamarcJci. In 1837 he applied to it two different names, Choristites Lamarckii, C. Wal- 

 cotti, and Enteletes. MM. de Verneuil and d'Eichwald, knowing nothing of the characters 

 of the fossil, described it by the name of Spirifer Lamarckii; and in 1876 von H. 

 Trautschold in his fine work ' Die Kalkbriiche von Mjatschkowa, eine Monographie des 

 oberen Bergkalks/ described and illustrated the exterior of the species under the name 

 of Orthis Lamarckii ; but none of the authors above named had been able to expose and 

 describe the interior characters of the fossil ; hence the confusion that ensued. 



As the genus Enteletes is but little known, it will be as well to describe its type. 



In external shape, Enteletes Lamarckii or octoplicata is wider than long and more 

 or less globular, rarely exceeding some 13 lines in length by 17 in breadth and 13 in 

 depth. The dorsal valve is generally very convex and especially so at the umbo, with 

 two large prominent median ribs and one, two, or three on each of the lateral portions 

 of the valve. The hinge-area is triangular, narrow, and sharply defined, about half the 

 breadth of the shell. The beak is much incurved. The ventral valve is less convex 

 than the dorsal one, with a deepened sinus, along the centre of which there exists an 

 angular rib, and one or two ribs on either of the lateral portions of the valve ; the area is 

 well defined, from 5 to 7 lines in length by one in height, and divided along the middle 

 by an open triangular fissure. The external surface of the valves is closely covered with 



