22 ME. M. LATIEIE ON THE 



attached in the middle of circular thin areas, while just in front 

 of this plate is a large bunch of simple bristles. 



In the membranous area, bounded below and at the sides by 

 the basal joints of the second pair of appendages, and at the 

 top by the carapace, lies the opening of the mouth (fig. 13, m.). 

 This is at the end of a short cylindrical tube, and is set round 

 with hairs. The tube is strengthened below by a small chitinous 

 plate with serrate anterior margin (fig. 13, m.t.s.), and above by 

 the stronger and more important epistoma or camerostome. 

 This epistome passes back through the membranous body-wall 

 and projects into the interior of the thorax as three spines which 

 reach as far back as the brain. These spines serve for the 

 attachment of muscles connected with the stomodseum. 



The rest of the ventral surface of the thorax is covered by 

 two sternal pieces and the basal joints of the three walking-legs, 

 which are fused to the body. The third appendage, which is 

 long and slender and tactile in function, is attached close under 

 the carapace to a membranous area Ijing between the second 

 and fourth appendages. The posterior sternal piece is a trun- 

 cated triangle in form, the posterior margin being bent up dorsally. 

 Just beyond the end of this bent-up portion is a separate trans- 

 verse piece of chitin, to which the dorso-ventral muscle from the 

 second dorsal sclerite is attached. 



The majority of the ventral abdominal sclerites want no special 

 description, being almost precisely similar to the dorsal ones. 

 This, however, is not the case with the first and second. The 

 first sclerite, which we may term the genital plate, covers the 

 ventral surface of the first two segments. The genital duct 

 opens behind it, and under it at each side lies the first pair of 

 lung-books. Bound the posterior margin the chitin is bent in 

 for a short distance in the middle line, but considerably more 

 towards the sides. There are no dorso-ventral muscles inserted 

 in this plate, those of the second tergite being, as mentioned 

 above, inserted in front of it. 



The second ventral sclerite (PI. IV. fi g. 14) corresponds to the 

 third tergite ; but owing to the great development of the genital 

 plate it lies somewhat behind its proper position. The third 

 ventral sclerite is narrower than the rest, for the same reason. 

 The second sclerite resembles the first in covering a pair of lung- 

 books which are situated at the sides, as well as in having the 

 posterior margin bent in. This bent-in portion is very narrow 



