I 
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A. T. EVANS 
Fig. 8 Sagittal section through head of Streptocephalus texanus, showing 
origin of flexor muscle of the second antenna; A, base of second antenna; B, 
ventral thickening of chitinous covering of body, in front of the mandible; C, 
cross section of base of mandible; D, flexor muscle of second antenna; /, thicken- 
ing of chitinous covering of body at origin of flexor muscle; F, one of the trans- 
verse muscles of head, in section; G, chitinous covering of body. 
Fig. 9 Para-sagittal section of head and base of frontal appendage of Tham- 
nocephalus platyurus, showing frontal organ of Claus; A, chitinous covering; 
B, frontal organ of Claus; C, base of the trunk of frontal appendage; D, a trans- 
verse muscle of head; HE, muscle of frontal appendage; F’, muscle of second antenna. 
