C. E. JBeecher — Koninckina and related Genera. 213 



It is further evident that the extremely young, or nepionic 

 shell, in all these genera, was biconvex in form, and furnished 

 with a well developed area and opening for the protrusion of 

 the pedicle, thus agreeing with the conclusions reached by J. 

 M. Clarke and the author in a study of Silurian brachiopods.* 



The perforation persists to maturity, but does not present 

 any increase in size, and is probably of little functional im- 

 portance. No additional increase takes place in the hinge area 

 so that the final development of these parts may be considered 

 as completed in the early neologic period, subsequent to which, 

 the enrollment of the beak serves more or less to conceal them. 



The calcareous spiral lamellae were first worked out by 

 Professor E. Suessf (see fig. 1), but the vascular markings 

 and spiral impressions on the interior of 

 the valves had been well described and 

 illustrated before by Dr. Woodward 4 



Nothing has been added since, except 

 the important discovery made by Herr 

 Zugmayer,§ that the lamellae are double, 

 both in the type species and in another 

 form from the Hallstatt Beds. 



The attachment of the primary lamellae 

 to the hinge plate is by two slender, diverg- 

 ing crurse, rising from the cardinal pro- Figure l.— Koninckina Le- 

 cesses nearly at right angles to the plane orihardi Wissm. Spiral 

 of the margin of the dorsal valve (see figs. la f ell <? and 7 su PP° rts > 



o j ns -n j.i • t i. i i ,i after Suess, local 



o and 9). Jbrom their distal ends, the 



primary lamellae originate and extend directly forward for a 



short distance, and then are abruptly curved laterally, and 



gently downward, forming the beginnings or bases of the 



spiral cones. At the point of curvature, two processes are 



given off, which are marked at their origin by a notch, thence 



extending inward, they are united at the central line forming 



the loop (figs. 5 and 8). The anterior portion of the loop is 



supported or articulated with the median septum of the dorsal 



to the apex of the cone. Both lamellae are free, and disposed 



then closely follow the four volutions of the primary lamellae 



the loop. They make an anterior curve in the middle, and 



are apparently connected with, the center of the ventral side of 



The secondary or accessory lamellae take their origin at, and 



valve, making a distinct facet, indicated by x, fig. 7. 



* Memoirs N. T. State Museum, vol. i, No. 1, Oct., 1889. The Development 

 of some Silurian Brachiopoda, p. 83. 



f Loc. tit., p. 83, tab. iii, fig. 256. 



j Manual of the Mollusca, p. 231, 1854. 



§ Noted by Davidson in British Fossil Brachiopoda. General Summary, p. 368, 

 1884. 



Am. Jotjk. Sci.— Third Series, Vol. XL, No. 23*7.— Sept., 1890. 

 14 



