PLATE IV 



Fig. 41. Labrum, Polyrmtarcys, dorsal as- Fig. 



pect. Fig. 

 Fig. 42. Labrum, Chirotenetes, dorsal aspect. 



Fig. 43. Labrum, Callibaetis, ventral aspect. Fig. 



Fig. 44. Labrum, Baetis, ventral aspect. Fig. 



Fig. 45. Labrum, Oligoneuria, dorsal as- Fig. 



pect. 



Fig. 46. Labrum, Ecdyurus, ventral aspect. Fig. 

 Fig. 47. Labrum, Hagenulus, ventral aspect. 



Fig. 48. Canines, Rhithrogena. Fig. 



Fig. 49. Right mandible Palingenia, after Fig. 



Eaton. Fig. 



Fig. 50. Lacinia, mandible Polymitarcys. Fig. 



Fig. 51. Lacinia, mandible Siphlurus. Fig. 

 Fig. 52. Lacinia, mandible Leptophyes. 



53. Lacinia, left mandible Heptagenia. 



54. Lacinial region, right mandible 

 Heptagenia. 



55. Lacinia, mandible Choroterpes. 



56. Right mandible, Lachlania. 



57. Labrum Ephemerella, ventral as- 

 pect. 



58. Right mandible Prosopistoma, after 

 Eaton. 



59. Lacinia, mandible Euthyplocia. 



60. Lacinia, mandible Baetis. 



61. Apex right mandible, Ameletus. 



62. Left mandible, Homeoneuria. 



63. Left mandible, nameless Chilean 

 nymph, after Eaton. 



34 



