798 On the Homologies of the ( ist tn Iamb. [October, 



or generalized nature of Limulus. While we have in another place 

 endeavored to show in the light of A. Milne-Edwards' anatomical 

 studies on Limulus, that it is an abnormal Crustacean and far 

 removed from the Branchiopoda ; there are nevertheless some 

 points in which it comes in contact with the Phyllopoda, and 

 which have been noticed ever since the time when O. F. Muller 

 comprised Apus in his genus " Limulus." If the reader will com- 

 pare the accompanying longitudinal section of Limulus with our 

 section of Apus in PI. xi, some striking resemblances will be seen; 

 externally the front edge of the carapace, i. e., the frontal dou- 

 blure, so well adapted for burrowing in the mud ; the relations of 

 the hypostoma or labrum, and the retention of the ocelli, as well 

 as the mode of molting the shell, are external, points of resem- 

 blance, while internally the front part of the head filled with the 

 lobules of the liver, the oblique long narrow, oesophagus, the 

 position of the stomach under the eye so far in front in the head, 

 the simple archi-cerebrum, the general form of the heart, and the 

 gnathobases near the mouth are additional points of resemblance. 



EXPLANATION OF PLATE XI. 



Enlarged 3 # times, md, 



