NEUROPTBRA— THYSANURA— BALLOSTOMA. 97 



discoverable on the most careful special search, unless such an office may 

 be performed bv long delicate hairs which seem, in some few instances, to 

 be scattered distantly over the projected mouth-tube. 



A special study of the buccal plates in the twenty-four or twenty-five 

 specimens which best show them gives no very satisfactory explanation of 

 their form and relations. They have been said to form a ring, because in a 

 considerable number they are so arranged ; but it may be doubted whether 

 this appearance is not due to the flaking of the chitinous part.s. Like the 

 lips of the notches of the thoracic segments, the buccal apparatus was evi- 

 dently more dense and thicker than other tegumentary parts, for these are 

 darker colored than the other parts and often carbonaceous. In this con- 

 dition the central portions seem liable to flake away and leave the thinner 

 edges with ragged fi-agments of the carbonaceous inner portions attached, 

 thus frequently forming a sort of irregular ring of dark chitine. On the 

 other hand, it is just as common for fragments to become chipped out from 

 the edges, or for rounded bits to fall out here and there, producing thereby 

 an almost endless variety of present appearances. Among these it is diffi- 

 .cu-lt to trace the clew to the original arrangement and form of the plates. 

 One might anticipate that these would have occurred around the central 

 orifice of a proboscis ; and if anything of this sort was present it would 

 appear the most probable (though extremely doubtful) that there were four 

 subtriangular plates of pretty large size, the lateral the larger, nearly meet- 

 ing by their tips at the center. From specimens, however, which are least 

 broken, it would seem quite as probable that the apparatus consisted of two 

 attingent or overlapping circular plates, placed transversely, densest cen- 

 trally, which by their consolidation form an oval rounded mass. How 

 such a pair of plates, or compound plates, could have subserved any pur- 

 pose in the procuring of food I can not understand, but that such is their 

 not unfrequent appearance, especially when seen through and pi'otected by 

 the thoracic shield of the first segment, is nevertheless the fact. It is to be 

 hoped that other specimens may set this matter at rest. Those at hand allow 

 no more definite statement than has been made. About three-fourths of 

 the specimens of this species show the buccal plates more or less distinctly. 

 In all but three they lie outside the body, usually at a distance from it of 

 about half the length of the first thoracic segment. In a fourth specimen 

 they lie half protruding at the front edge of the body. 



VOL XIII 7 



