29 (28) Carapace longer than broad, front strongly tridentate in dorsal view Porcellana sigesbiana 



Figure 62. — Porcellana sigesbiana: carapace, and 

 chelae (twisted to show tooth pattern). 



30 (24) Frame of mouth elongate and triangular, sides converging anteriorly 



Subsection Oxystomata 3 1 



30 (24) Frame of mouth either rectangular (prolonged in certain swimming crabs) with sides 



parallel, or transversely somewhat ellipsoid or kidney shaped 33 



Figure 63. — Brachyuran mouth frames; A, triangular; B, rectangular; C, kidney-shaped or 



transversely ellipsoid. 



31 (30) Carapace very short, exposing first 2 or 3 abdominal terga in dorsal view; front with 



2 bifid (appear as 4) laminar teeth Family Dorippidae Ethusa microphthalma 



Figure 64. — Ethusa microphthalma. 

 portion of body in dorsal view. 



31 (iO) Carapace not so short, exposing little if any of abdomen in dorsal view 



23 



32 



