444 



STUART WELTER 



perhaps to be compared with Girtyella as the genus most closely 

 allied to it. If the concave hinge-plate of Girtyella, which is sup- 

 ported by a median septum, be depressed along its median line to 

 such an extent that the concave plate itself rests directly upon the 

 floor of the valve, the median septum being eliminated, then we 

 would have essentially the characters shown in this genus. The 

 bisinuate folding of the anterior portion of the pedicle valve may 

 be a generic character, but this cannot be determined from the 

 single species so far recognized. 



Genotype. — D. bisinuata n. sp., St. Louis (?) oolite, Lewis 

 County, Mo. 



Cranaena Hall and Clarke 

 Description. — Shell terebratuliform. Pedicle valve with or 

 without a median sinus and with well-developed dental lamellae 



Q 



6 c 



^x 



v-y 



Fig. 4. — A series of ten cross-sections (X25) of the rostral portion of the shell of 

 Cranaena ioivensis (Calvin), from all but the first of which the pedicle valve has been 

 omitted. 



Fig. 5. — A series of six cross-sections of the rostral portion of the brachial valve 

 of Cranaena sp. undesc, residual chest, Springfield, Mo. 



of moderate length internally, the foramen large, oblique, and 

 encroaching upon the umbonal portion of the valve, the beak 

 incurved. Brachial valve without median fold, even in those 

 species with a well-defined sinus in the opposite valve, but some- 

 times with a slight mesial depression near the front margin ; inter- 

 nally the well-developed socket-plates are connected transversely 



