C. M Beecher — Koninckina and related Genera. 215 



placed with Productus. In the same paper, Swallow describes 

 a Productus with a like specific designation {P. Americanus), 

 and to avoid duplication, the name Productus Swallovi is here 

 proposed for the species described as Koninckina Americana. 



Anvphiclina, Laube, 1865.* — This genus agrees very closely 

 in all its essential features with Koninckina, so far as can be 

 observed from the material studied. The hinge and beak char- 

 acters, represented in fig. 2, differ little from those shown by 

 the young of Koninckina, except that the area is higher, and 

 the delticlial plates well developed. This last condition is ex- 

 plained by the erect position of the beak, which in that genus 

 is so much incurved as to prevent the normal growth of delti- 

 dial plates. 



Xearly ail well-preserved specimens, both of the type species 

 A. dubia Minister and A. Suessi Laube show distinctly the 

 existence of spirals, and several sections have been made pre- 

 senting features similar to those represented in fig. 6 of 

 Koninckina, in which the primary and secondary lamellae and 

 the position of the apex of the cone are well displayed. Fig. 

 1 is of a young specimen in which the lamellae on the left side 

 have become displaced so that a double series of spirals results, 

 while on the right side they are superimposed in their usual 

 position. Fully matured individuals have four volutions in 

 the ribbon as in the preceding genus. The attachments of the 

 lamellae could not be made out distinctly, but they apparently 

 offer no peculiar features. 



From the position and size of the spiral cones, it is evident 

 that the impressions described by Laube (loc. cit.) as muscular 

 scars, on the interior of the dorsal valve, must be otherwise con- 

 sidered ; and it is naturally inferred that they represent ridges 

 and furrows limiting the brachial regions, the diverging cardi- 

 nal processes, and the vascular impressions. The parts about 

 the interior of the dorsal beak agree with those represented in 

 fig. 7 for the preceding genus. 



It is therefore apparently necessary to deal with Amphiclina 

 and Koninckina as very closely related forms, and undoubtedly 

 belonging to the same patronymic group. 



The first consideration of genera related to this group 

 naturally deals with such forms as have previously been 

 grouped with the Koninckinidae. Only the classifications pro- 

 posed by a few of the leading authorities need be discussed in 

 this place. 



Davidson, in his Introduction to the Classification of the 

 Brachiopoda, 1851-54, p. 92, proposed the family Koninckin- 



*Die Fauna der Schichten von St. Cassian, II Abtheilung, p. 28, 1865. 



