282 PROCEEDINGS OF TEE NATIONAL MUSEUM. 



Family PIJSTNOTHEEID^. 



Genus THAUMASTOPLAX Miers. 

 THAUMASTOPLAX ANOMALIPES Miers. 



Thmimastoplax anomalvpes Miers, Ann. Mag. N. H. (5), VIII, 1881, p. 261, pi. xiv. 

 fig- 2. 



West African locality. — Goree Bay, Senegambia, 9 to 15 fathoms 



(Miers). 



Tribe CYCLOMETOPA. 

 Family POTAMONID^. 



KEY TO THE WEST AFRICAN GENERA AND SUBGENERA OF THE FAMILY POTAMONID^. 



A. Ambulatory legs with anterior margin of carpal and propodal joints unarmed. 



B. Lateral margin of carapace armed with large and sharp teeth or spines. 

 ■; > Genus Parathelpliusa. 



B'. Lateral margin of carapace entire, toothed or granulate Genus Potanion. 



C. Postfrontal crest present and uninterrupted Subgenus Potamonauies. 



C. PostfrontaL crest absent Subgenus Geothelphusa. 



A'. Ambulatory legs armed with numerous spines on the anterior margin. 



Genus Erimetopus . 



Genus POTAMON Savigny. 

 Subgenus POTAMONAUTES MacLeay. 



KEY TO THE WEST AFRICAN SPECIES OF THE SUBGENUS POTAMONAUTES. 



A. Lateral margin of carapace with a tooth between the outer orbital tooth and 

 the postfrontal crest. 



B. Postfrontal crest terminating in a well-marked tooth africanus. 



B'. Tooth rudimentary or wanting. 



C. A groove separates the postfrontal crest from the lateral margin of the cara- 

 pace - aubryi. 



C. Postfrontal crest and lateral margin continuous decazei. 



A'. Lateral margin of carapace without a tooth between the outer orbital tooth and 

 the postfrontal crest. 

 B. Epibranchial tooth strong, produced. 



C. Postfrontal crest arcuate, more advanced at its middle than the epibranchial 

 tooth. 



D. Carapace very thick, swollen hayonianus 



D'. Carapace less thick, swollen; front narrower; a deeper sinus between the 



postfrontal crest and the epibranchial tooth dtihins. 



C. Postfrontal crest sinuous, its middle portion about equally advanced with 



the epibranchial tooth hallayi. '■ 



B'. Epibranchial tooth nearly obsolete, not produced. 



C. Carapace flattened ; postfrontal crest not prominent margaritarius. 



C. Carapace very convex. 

 D. Postfrontal crest sloping backward from the middle to the lateral mar- 

 gins perlatus. 



D'. Postfrontal crest sinuous anchieta: 



' According to the figure of this species, the jjostfrontal crest is uninterrupted. 



