MAGAS. 23 



presenting this peculiarity; but I have since observed, as above stated, that specimens did 

 really at times assume the aspect of Sowerby's figures, and varied even to a greater 

 extent. 



I cannot understand what can have induced M. D'Orbigny to place in the family of 

 Magasidce the genus Terebratulina, which is completely and widely separated from Magas 

 by its internal arrangements, as may be seen by casting a glance to the interior of Caput 

 Serpentis, or to that of any other species of the genus. If Terebratulina is admitted to 

 belong to the same family as Magas, I see no reason why all the others with calcareous 

 appendages should be separated, several having much more important family affinities ; 

 the only reason stated by M. D'Orbigny being based on the erroneous supposition, that 

 Terebratulina was unprovided with a deltideum. I have elsewhere shown that it really 

 exists to a greater or less extent in all the species of that genus, and particularly on 

 T. substriata Schlotheim, an Oolitic form, possessing the true internal character of 

 Terebratulina, but rejected and placed by M. D'Orbigny in that of Terebratula, from the 

 well-developed deltideal plates, proving how dangerous it is to class certain shells from 

 mere external appearances, without giving full weight to the far more important internal 

 arrangements connected with the disposition and the organisation of the animal. 



Magas pumilus, to my knowledge, has not been observed lower down than the Upper, 

 and perhaps Lower Chalk ; it was found at Maudesly by Mr. Sowerby, at Trimmingham by 

 Mr. Bowerbank, at Norwich by Mr. Fitch and the Rev. Mr. Image, at Brighton by 

 Mr. Catt, and at Letheringsett, West Norfolk, by Mr. C. B. Rose, &c. On the Continent 

 it is abundant; at Meudon near Paris, at Sens, Fecamp, near Valogne, and St. Gervais near 

 Epernay in France, at Vaclo in Belgium, Simbrisk in Russia, &c. 



Plate II, fig. 1. From the Norwich Chalk, in my Collection, enlarged. 



„ fig. 2. A specimen, in which the smaller valve is slightly concave. 



„ fig. 3. From the Chalk of Norfolk, in the British Museum, showing a very 

 thickened margin and adult shell. 



„ fig. 4. From the Chalk of Trimmingham, in the Collection of Mr. Bowerbank. 



,, fig. 5. From my Collection. 1 



„ fig. 6. In the Collection of British Museum. 



1 Some of my friends urged me to make two species out of all these forms of Magas, from the 

 extraordinary difference presented between such specimens as fig. 1 and figs. 7, 8 ; but I should be puzzled 

 where to draw a line of demarcation, when it is remembered that figs. 7, 8, and 33, as well as 10 and 1 1, 

 are quite exceptional forms, arising, no doubt, from malformations and accidental causes ; besides which, 

 Mr. Sowerby's type of Magas pumilus was created on specimens such as figs. 2, 4, and 5, which are inter- 

 mediate in shape between those extremes in which the beak is much incurved, and those that are not so 

 disposed. I consider figs. 1, 2, 3, 4, and 5 the usual forms of Magas pumilus, the remaining figures 

 being accidental malformations. The illustration of Magas pumilus, given by M. D'Orbigny, in the work on 

 Russia and the Oural, pi. xliii, fig. 27, closely resembles the real type of this species as figured by Sowerby, 

 and is similar to our fig. 4 ; in it, as maybe observed, the smaller valve is slightly convex and not depressed; 

 the beak is likewise not much recurved, showing the area and foramen in all its extent. 



4 



