at idae , ▁T rip ter oc er at idae , ▁and ▁Val cou ro cer at idae ▁( F lower ▁ 1 9 5 0 ). ▁ ▁In cluded ▁gener a ▁The ▁G rac il oc er at idae ▁contains ▁five ▁known ▁gener a , ▁four ▁of ▁which ▁are ▁briefly ▁described ▁in ▁the ▁Tre at ise ▁Part ▁K , ▁N aut ilo idea - On c oc er ida . ▁The ▁fifth ▁and ▁last ▁listed ▁was ▁named ▁in ▁ 2 0 0 9 . ▁They ▁are ▁as ▁follows ▁with ▁their ▁origin ators : ▁▁ ▁G rac il oc eras ▁F lower ▁ 1 9 4 3 : ▁sl ender , ▁com pressed , ▁regularly ▁expand ing , ▁body ▁chamber ▁much ▁longer ▁than ▁ph rag mo con e ; ▁sept a ▁very ▁close ▁spac ed , ▁si ph un cle ▁small , ▁sub vent ral ; ▁M - U ▁Ord , ▁N Am . ▁( S weet ▁K 3 8 3 ) ▁▁ ▁E or iz oc eras <0x09> F lower ▁▁ 1 9 4 3 : ▁rapidly ▁expand ing , ▁ap ically ▁cur ved , ▁ad or ally ▁straight , ▁faint ly ▁com pressed ▁with ▁o void ▁cross ▁section ; ▁s ut ures ▁straight , ▁slightly ▁ob lique ; ▁exterior ▁with ▁trans verse ▁bands ▁and ▁fine ▁longitud inal ▁mark ings ; ▁no ▁hy pon omic ▁sin us ; ▁si ph un cle ▁small , ▁vent ral . ▁M ▁Ord ▁ ▁N Am . ▁( S weet ▁K 3 8 3 ) ▁▁