212 C. E\ Beecher — Koninckina and related Genera. 



ascertaining for the first time, so far as known, the true char- 

 acter of the internal brachial supports. They have been quite 

 fully determined for Koninckina, and their presence is here 

 first demonstrated in the genus Ampliiclina. 



Koninckina Suess, 1853. — The general form and characters 

 of this genus, as represented in the type species [K. Leonhardi 

 Wissmann sp.), have been so frequently described by various 

 authors as to necessitate no restatement in this place. The 

 features which require further consideration are : the develop- 

 ment of the hinge and beak, the internal calcareous brachial 

 supports, the development of the spiral lamellae, and the interior 

 of the dorsal valve. 



The beak has uniformly been described as imperforate and 

 the hinge without an area.* This statement has come from 

 the examination of fully mature individuals measuring S mm and 

 upwards in length, in which these characters are so obscure, or 

 involved, as to escape notice, without having previously care- 

 fully noted the characters presented by the young. In speci- 

 mens 5 mm or less in length, the enrollment of the beak has not 

 proceeded so far, and a study may be made of its principal 

 features, proving the existence of the parts said to be wanting, 

 and bringing the genus into more general harmon}*- with the 

 articulates. 



Figure 3 shows the umbonal and hinge characters which can 

 be observed in a specimen about 4 mm in length. The initial 

 dorsal valve is shaded in the figure, and is the only convex 

 portion of the valve, as succeeding growth produces a concave 

 shell, making the concavity very pronounced in full-grown 

 shells. It is evident that the growth-stages between the con- 

 vex and concave form were much accelerated, as the line of 

 demarkation is abruptly outlined with the completion of the 

 nepionic stage. 



The hinge is narrow, extending to the cardinal extremities. 

 In the center is a triangular area, partially closed by a slight 

 deltidial growth or deflection at the margins, and the apex of 

 the ventral valve is perforate. The dorsal valve shows a much 

 narrower hinge, and under the beak a slight callosity extend- 

 ing into the open area below. It will at once be noticed 

 that the young, or neologic, stages of growth in Koninckina 

 correspond to the adult, or ephebolic, conditions in Ampliiclina 

 and Koninckella. 



* Classification der Brachiopoden von Thos. Davidson, E. Suess, 1856, p. 93, 

 "keineArea; kein Deltidimn ; keine Durchbohrung am Schnabel." Manuel de 

 Conchyliologie (Fischer) Brachiopodes by D. CEhlert,'1887, p. 1292, "Sans area 

 ni deltidium." 



