88 K. KISHIXOUYE. 



Al-^o after the corresponding structure of the Trilobites, I name tlie 

 furrow which separates the median lol^e from, the fir.^t lateral lohe as 

 the axial fiuroiv. and the suture lietween the first and the second 

 lateral lohes as the facial suture. 



It is remarkahle that in Limuhis the si^ine-!, movaljle aiid immov- 

 able, are found on the facial suture of the céphalothorax and tlie marü-in 

 of the ahd(mien, and within these boundary lines only (figs. ir-I\^). 



It is also very remarkable that the eyes are f~)und below the f icial 

 suture oidv. The Trilobites, in which the ficial sutures of both sides 

 ffenerallv do not meet in the dorsal median line, have no median eves 

 (fig. V). Harpes among the Trilobites, and Liiniihts in which the 

 facial sutures of both sides meet in the dorsal median line, have the 

 median eye.'^. 



In some Trilobites such as Mglina, the free cheeks are not well 

 developed ; they ara not seen from above, hence the lateral eyes are at 

 the lateral margin of the ce])halt)tliorax. In these forms the fixed 

 cheeks are al^^o very feebly deveh^ped. I regard this type, which is 

 found in most Arthropods as the ]")rototype of the co] »lia lotliorax. 

 In Phacops eic, tlie free cheeks are a little seen from the dor.^al side. 

 In the majoi'ity of the Trilobites the ïree cheeks are well developed at 

 the lateral sides of the fixed cheeks ; and in Harpes and J.liii'iln.'< they 

 are enormously developed, at the lateral sides as well as in fn^nt of the 

 fixed cheeks. In these animals the céphalothorax is mucli broader 

 than the abdomen. 



In the ventral surface of the alxlominal sliield of Liiiiuliis we find 

 a region (figs. III. IV, /r.' cli.') corresponding to the free cheek of the 

 céphalothorax. It is an elevated portion of the lateral edge. 



The development of the eyes, which I have described aljove, 

 shows that thev (both lateral and median eves) arise from ])ain'd 

 epiblastic thickenings, just at the margin of the epiblast of the ventral 



