Raymond : Rrachiopoda and Ostracoda of thk Chazy. 235 



shell, and then concave. Brachial \al\e tlal on the iimlm and convex 

 in front. Cardinal area narrow, the wide dellhyrimn mosily covered 

 by the deltidium, with a small ojiening for the i)ediclc at the beak. 

 Muscle area in the pedicle vaKe small, confiiK-d lo the space unflcr the 

 umbo. Surface marked by fine alternatint; stria', the prominent stria; 

 being very numerous and increasing by implantation. Between each 

 pair of the strong stri;e are two or three finer ones, and the whole sur- 

 face is crenulated by very fine concentric stride. The brachial \al\e 

 sometimes shows some fine concentric wrinkles. 



One specimen is 15.5 mm. long and 20 mm. wide. Another is 16 

 mm. long and 19.5 mm. wide. 



Locality. — All the specimens are from the lower layers on Valcour 

 Island, and are in the Carnegie Museum. 



Family ORTHID.E Woodward. 



Genus Orthis Dalman. 



18. Orthis costalis Hall. 



(Plate XXXV, figure 4.) 

 Orthis costalis Hall, 1847. Paleontology of New York, Vol. I, p. 20, PI. 4 bis, 



fig. 4a. Non 46, 4b, 4c. 

 Orthis costalis Hall, 1883. Second Annual Report New York State Geologist, 



PI. 34. fig- 35- 

 Orthis costalis Hall and Clarke, 1892. Paleontology New York, Vol. \'ni, 



pt. I, PI. 5, figs. 16, 17. 



This species is generally listed as one of the commonest and most 

 characteristic brachiopods of the Chazy, but the writer has only seen 

 one specimen which he was sure belonged to the species, and that 

 the specimen represented in figure 4a on the plate accompanying Hall's 

 original description. Through the kindness of Dr. Hovey I have been 

 able to study the types of this species, preserved in the collection at 

 the American Museum of Natural History. The original of figure 4a 

 is undoubtedly an Orthis. It is a pedicle valve with about thirty-two 

 simple plications. The hinge is nearly equal to the greatest width, 

 and the shell is nearly as long as wide (11 X 13 mm.). 



The original of Hall's figure 4c — the smaller of the specimens marked 

 46 on the plate — is an exfoliated pedicle valve of a Plectorthis. This 

 specimen is on a small fragment of limestone with numerous other 

 brachial and pedicle valves, all of which belong to Plectorthis e.xfoliata, 



