STALK-EYED CRUSTACEA 47 



I. Tyche. 



Tyclie .... Miers, A. Milne Edwards, Bell. 

 PlatyrhyncJius . Desbonne and Schramm. 



Carapace produced behind and laterally. The rostrum 

 composed of two diverging horns. The praeocular spines 

 extend forwards and outwards beyond the rostral spines. 

 The superior orbital order is developed laterally, almost 

 hiding the eyes. There is no orbital floor. The external 

 antennae are hid under the rostrum ; their basal joint 

 is wide, and its antero-external extremity forms a small 

 blunt point ; the succeeding joints are cylindrical. The 

 fourth joint of the external maxillipedes is dovetailed 

 into the third in an S-shaped joint ; the internal margin 

 of the third reaching almost to the summit of the fourth 

 joint. 



The first pair of legs is little developed. The walking 

 legs are thin, and have a much curved terminal joint. 



Range. — East and West Coast of America ; in shallow 

 water. 



I. Tyche emarginata. 



Tyche emarginata .... White, Stimpson, A. Milne 



Edwards. 

 Platyrhyiichus tritiibcrculatus. Desbonne and Schramm. 



The carapace is prolonged backwards into two flat 

 lobes. The gastric region is on a more elevated plain 

 than the front ; it has three tubercles, two anterior and 

 one posterior and median. There is a large tubercle 

 on the anterior branchial lobes ; a strong tuberculous 

 crest extends upon the lateral border of the branchial 

 regions. The cardiac lobe has three tubercles. 



