MOLLUSCA—PELECYPODA. 373 



summit CXXXIV. Astartella. 



20". Cardinal teeth not bifid CXXXVII. Astarte. 



23-f. Beaks small, appressed 23*. 



23*.- Umbonal ridge present 21" . 



2i n '. Length and height subequal. 



CXXXII. Cypricardella. 

 2i n ' . Length much greater than height. 



CLXXIX. Saxicava. 

 23*. Two weak umbonal ridges present, an anterior and a 



posterior CLXXIII. Solyma. 



23*. Umbonal ridge absent CLXXX. Panopea. 



xx. Shell subtriangular 24-f-. 



24-f. Strong umbonal ridge present, running from beak to pos- 

 terior basal angle 24*. 



24*. Beaks exceedingly prominent, strongly incurved ; promi- 

 nent concavity beneath the beaks.. CXXXVIII. Opts. 



24*. Beaks not exceedingly prominent 22 //f . 



22 // . Cardinal teeth (6-8) radiating fan-like from beneath 



the beaks LXXXVIII. Lyrodesma. 



22 ,f . Cardinal teeth two in right valve, three in left ; 



teeth more or less transversely striated 0" . 



o n ' . Surface with rows of nodes XC. Trigonia. 



o n '. Surface not nodose LXXXIX. Schizodus. 



22". Cardinal teeth two in each valve .p". 



/". Pallial line simple 6 //r . 



6 /// . Inner margins of valves dentate. 



CXXXIX. Crassatellites. 

 6 f,f . Inner margins of valves not dentate. 



CXL. Etea. 



p" '. Pallial sinus present y /// . 



y fff . Lateral teeth prolonged d f// . 



d ,ff . Resilifer present j>). 



3). Resilifer elongate CLXIX. Semele. 



3). Resilifer spoon-shaped. 



CLXX. Cumingia. 



d'". No resilifer present CLXVL Tellina. 



7 //V . Lateral teeth minute if any. 



CLXVIL Mnona. 

 22 n '. Cardinal teeth two in right valve, one in left. 



CLXXVIII. Corbula. 



24f. Shell without strong umbonal ridge 25*. 



25*. Surface radially striate CXVIII. Crcnella. 



25*. Surface without radial striae 2j f/ . 



23". Beaks exceedingly prominent, strongly incurved. 



LXXVIII. Aucella. 



23". Beaks but moderately prominent q n '. 



q n '. Cardinal teeth one in each valve; no resilifer 



present # CLII. Tancredia. 



q n '. Cardinal teeth two in each valve. 



CXXXVII. Astarte. 

 q". Cardinal teeth, two in right valve, one in left...<5' /// . 



