CEPHALOPODA— ORTHOCHOANITES. 



lOI 



with ventral, lateral and dorsal lobes, but no annular lobes. Car- 

 bonic-Triassic. 



124. T. cavatum Hyatt. (Fig. 1324.) Carbonic. 

 Tubercles round and blunt, about two camerae apart; ventral 



tubercles faint; spaces between tubercles flat, or scarcely concave. 

 Coal Measures of Texas. 



125. T. occidentale (Swallow). (Fig. 1325.) Carbonic-Permic. 

 More robust than preceding, with coarser, somewhat elongate 



tubercles on ventrolateral angle, and the inner row of tubercles 

 faint or almost obsolete, the space between the two being wider 

 than in the preceding. Ventral rows of tubercles strong, rounded ; 

 all spaces between rows of tubercles concave. (= T. quadran- 

 gulum McChesney, type of genus.) 



Coal Measures of Illinois, Iowa, Missouri, Kansas, Nebraska, 

 Texas, Pennsylvania and West Virginia; Permic of Kansas and 

 Texas. 



KONINCKOCERATIDA. 



XLIV. DoMATOCERAS Hyatt. 



Nautilicones with slightly impressed zone in adult; biangular in 

 young; whorls tetragonal in section; surface smooth; sutures with 

 marked umbilical saddles ; siphuncle ventral of center. Carbonic. 



Fig. 1326. 



Domatoceras lasallense, two views of a fragment, X 

 and Worthen, 111. Geol., V.) 



(After Meek 



