BRACHIOPODA. 
239 
and the formation of an umbonal or subrostral vault supported by a median 
septum. 
The geological range of both Clitambonites and Hemipronites is limited to 
the Lower Silurian. In American faunas the latter group is still unknown, 
and the former is represented by only two species, Orthisina Verneuili (von Eich- 
wald), Billings, from the Trenton limestone and the Anticosti fauna, and 
Hemipronites Americana, Whitfield, a closely allied species, from the Galena 
horizon of the Trenton, in Wisconsin. 
Polyt(echia, sub-gen. nov. Plate vii a, figs. 26-30. 
1886. Hemipronites, Whitfield. Bulletin American Museum of Natural History, vol. i, No. 8, p. 300, 
pi. xxiv, figs. 1-5. 
This name is proposed for the species Hemipronites apicalis, Whitfield, the 
essential characters of which have been clearly demonstrated by that author. * 
Mr. Whitfield recognized the distinctive character of this fossil but hesitated 
to propose a new generic term, which circumstances now require. 
_ 
Fig. 11. Polytcechia apicalis. Fro. 12. Polytcschia apicalis. 
Transverse section of pedicle-valve, near the apex. Transverse section near the cardinal margin. 
Diagnosis. Shell small, subtrihedral in contour. Hinge-line straight, about 
equaling the diameter of the shell. Pedicle-valve with a high, nearly verti¬ 
cal cardinal area marked with oblique striations parallel to the lateral margins. 
* In a provisional list of the genera of palaeozoic brachiopoda, published in the Eighth Annual Report 
of the State Geologist (p. 44, 1889), the name Waagenia was used with the intention of applying it to this 
sub-genus, but it appears that both Waagenia and Waagenella are preoccupied terms, therefore preclud¬ 
ing this intended expression of esteem and appreciation for the invaluable services of Dr. Waagen in this 
department of science. 
