86 
PALAEONTOLOGY OF NEW YORK. 
Genus MICKWITZIA, Schmidt. 1888. 
1888. Mickwitzia, Schmidt. Ueber eine neuendeckte untercambrische Fauna in Estland; Mem. de 
l’acad. imp. des Sciences de St. Petersbourg, vii Ser., tome xxxvi, No. 
2, p. 24. 
Diagnosis. Shells large, thick, unequivalve. Dorsal valve flat, circular; 
ventral valve oval, convex, produced 
into an acute apex, beneath which lies 
a triangular, more or less distinctly 
developed cardinal area. Valves 
not (?) articulated. Shell-substance 
composed of thin coarsely punctate 
layers alternating with prismatic 
laminae which are traversed by scattered vertical canals. Surface covered with 
radiating striae. Shell composed of calcic phosphate. 
Type, M. monilifera, Linnarsson. 
This name has been proposed by Dr. Schmidt for a shell which had been 
described by Linnarsson in 1869, # from the Eophyton sandstone, the oldest 
fossil-bearing formation of Sweden, and referred at that time to the genus 
Lingula (?),; subsequently by the same author in 1871,f to Obolus (?). More 
abundant material found near Reval has shown various features which have led 
to its establishment as a separate genus. The shell has the general appearance 
of Obolus, and its relationship to this genus is shown in the external charac¬ 
ters, and the grooved cardinal area. Unfortunately none of Dr. Schmidt’s 
specimens give a satisfactory indication of the internal characters, so that the 
generic value of the species must still remain in great doubt. A remarkable 
feature is shown in a single figure of the interior of the smaller valve, viz , a 
single large tooth-like process, situated centrally behind the beak, and bent at 
a sharp angle backward into what would have been the umbonal region of the 
opposite valve.| Dr. Schmidt is not convinced that this is to be regarded as a 
Mickwitzia monilifera. 
After Schmidt. 
Fig. 42. Pedicle-valve. Fig. 43. Interior of same valve. 
Fig. 44. Exterior of brachial valve. 
* dfvei’i af K. Vetensk. Akad. Forhandl. p. 344, t. vii, figs. 1, 2. 
t Kongl. Svenska Vetensk. Akad. handlingar, Bnd. 9, No. 7, p. 9, pi. i, figs. 2, 3. 
J Schmidt, pi. ii, fig. 16. 
