370 Viscount d'ARCHiAC and M. de Verneuil's 



but we think there is reason to preserve these species, particularly the last, which differs notably in the 

 beak and the area. 



3. Spirifer mediotextus, nob.. Tab. nost., XXXV. f. 9, 9 a, 9 6, 9 c. 



Shell depressed, semilunai-, ventral valve covered with radiating ribs, which are simple, slightly undu- 

 lated, twenty-four to twenty-six in number on each side, and which become narrower and more 

 close-set as they approach nearer to the extremities of the hinge. Beak slightly recurved upon the 

 area. In place of a varix there is a slight depression covered by a very delicate net-work, forming 

 longitudinal and transverse capillary striae. This net-work is not prolonged to the beak, although the 

 groove reaches the latter part. Dorsal valve more ventricose than the ventral, and having the same 

 number of folds similarly placed. Area large, very slightly concave. Upper angle 125°. Beaks 

 scarcely recurved. Aperture triangular, wide. Sinus large, flat, and covered with a net-work si- 

 milar to that of the other valve. Front presenting a double depression, and the junction of the valves 

 at this part forming a simple, straight and horizontal line. This latter character is not yet known 

 in any other species of the genus. Length of the hinge, 40 millim. ; of the shell, 24 ; thickness, 16. 



Refrath ; very rare. 



4. Spirifer cheiropteryx, nob.. Tab. nost., XXXV. f. 6, 6«, 6 b. 



Shell winged, very short, valves equally ventricose. Ventral valve divided into three parts by two 



elevated ribs, which set off from the beak and confine between them a rather indistinct varix. Two 



or three obsolete folds on each side. Beak slightly prominent, and touching the hinge. Lateral 



edges very concave, prolonged into wings. Dorsal valve divided by two ribs, similar to those of the 



other valve. Area very long, narrow, concave. Aperture triangular, extending from the beak to 



the hinge. Beak slightly recurved. Median sinus wide and deep, marked with pliciform striae of 



growth, like the rest of the surface. Front presenting a broad and deep fold, whose edges, resulting 



from the junction of the dorsal and ventral ribs, are unequally prolonged in the direction of the ribs. 



Length of the hinge, 27 millim. ; from the beak to the inner angle of the front, 1 1 ; thickness, 7. 



The two ribs are so developed upon each valve that these latter are divided into three concave lobes. 



The species is no less remarkable for this character than for the great length of the hinge. In the only 



two specimens we know, the prolongation of the ribs is unequal, and the shell represents pretty well the 



extended wing of a Bat. This disposition of the ribs and the pliciform striae of growth recal to mind 



what is seen in T, trigonella. (Schlot., de Buch, Mem. Geol. Soc. France, t. iii. p. 189. PI. XVII. f. 2.*) 



We have found in the mountain limestone of Vise, a shell which seems to be only a variety of S. chei- 



nypterijx. It is less transverse, the area is more elevated, the ribs are less prominent and less prolonged 



beyond the front, and lastly the folds and the striae of growth are more distinct than in our specimens 



from Paffrath. 



Paffrath ; very rare. 



5. Spirifer heteroclitus, de Blainv., Malac, PI. L. f. 3. De Buch, Mem. Geol. Soc. France, iv. PI. VIII. 



f. 11. Calceola heterodita, Defr. Diet, des Sc. Nat., Pianche Ostracees et Conchacees, f. 3. 

 We possess only a cast of this species : it comes from Villmar, where it appears to be very rare. Sp. 

 heterodita is found also in the Eifel and in Devonshire. 



6. Spirifer trapezoidalis, Cyrtia trapezoidalis, Dalni., Acad. Holm. 1827, PI. III. f. 2. Id. Bronn, Leth. 



supra, PI. III. f. 2. De Buch, loc. dt. Geog., PI. VIII. f. 12. 

 This species is found at Paffrath, according to de Buch. 



7. Spirifer glaher. Sow. Min. Conch., PI. CCLXIX. f. 1, 2. Variety minor, nob. 



This shell, very abundant in certain beds at Paffrath, seems to be the miniature of the »S^. glaber, which 



