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Section Stenoarca n. sect. 



Et.ymolo~:y »- Treves - narrow; Area . 



Shell small, reticulately sculpt rel; imbones almost terminal, 

 strongly proso^p-^^rate ; cardinal area narrow, irapreGsed, long, en- 

 tirely or almost entirely opisthodetie; hinge-teeth in two series, 

 the anterior, series short, thickened, more or less irregxilar, suh- 

 tmibonal in position, the upper thickened margin ceasing abruptly 

 behind the um.bo : posterior series longer and normal; the two ser- 

 ies continuous or interrupted by the evanescence of the teeth at the 

 anterior end of the posterior series. 



T ;pe .- A. dentera n. sp. 



Three new species are referred to this section; of these 

 dentera and suboandeida have an uninterrupted series of teeth, 

 ^rf-th the anterior series notably thickened, while adult indivi- 

 duals of modioleida usu.ally have a medial, vade e''"'entulons area. 

 A. subgandei'ia has a very snail portion of the cardinal area before 

 the umbones and in the case of the other tv/o species the cardinal 

 area is entirely opisthodetie. From the above s-^atements it is 

 evident that this section Is not sharply differentiate^!, but forms 

 an intergrading series "lith other sections. The shape of dentera 

 and §'^bcandeida suggests Jalloarca ; in shape and in the oossess- 

 ion of an interrupted dental series modioleida resembles Jalloarca 

 and also Oucullaria, but the cardinal area does not extend in front 



