48 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



coxae (fig. 18 B). In the adult grasshopper they form the ventral rims 

 of the coxal cavities, that of the mesothorax becoming a weakly 

 sclerotized plate, that of the mesothorax a membranous fold. The 

 definitive sterna of the pterpthorax in the Acrididae, therefore, do not 

 appear to contain subcoxal laterosternal elements as integral parts of 

 their areas. In the adult of Dissosteira the pleuro-sternal suture 

 (fig. 30 A, r) is obsolete in the mesothorax anterior to the coxa, but 

 remains distinct in the metathorax. 



Ppct 



Fig. 30. — Pterothoracic sterna and the base of the abdomen of Dissosteira. 



A, general view of pterothoracic sterna and first two abdominal sterna. 

 B, diagram of probable structure of mesosternum. C, diagram of probable struc- 

 ture of metasternum. D, diagram of structure of first abdominal sternum. 



acs, antecostal suture of first abdominal sternum ; Bs, basisternum ; C.v, coxa ; 

 CxC, coxal cavity ; IS, IIS, first and second abdominal sterna ; /, prepectal 

 suture ; k, furcal suture ; Pc, precosta ; Ppct, prepectus ; r, r, pleuro-sternal 

 sutures ; sa, sa, roots of sternal apophyses ; SI, sternellum ; t, t, inf ra-coxal lobes 

 of metasternum. 



The mesosternum of Dissosteira is a broad plate (fig. 30 A, Bs2, Sh) 

 bounded laterally by the obsolete lines of the pleuro-sternal sutures 

 (f) and the rims of the coxal cavities. Its anterior edge is slightly 

 convex ; its posterior border is deeply emarginated to receive a median 

 rectangular extension of the mesosternum {Bsz) which is dove-tailed 

 into the mesosternal notch. A prominent transverse suture {k), which 

 forms internally a ridge through the bases of the sternal apophyses 

 and extends laterally toward the coxal cavities (fig. '^i, k, k) is coin- 

 cident with the posterior edge of the median part of the sternum and 



