no. 1480. SCHIZOPOD CRUSTACEANS— ORTMAXX. 29 



(2) In the absence of the two pairs of oblique keels on the superior 

 face of the carapace. 



(3) In the shape of the ventral epimeral plate of the sixth abdomi- 

 nal segment, which, although closel} r approaching the shape seen in 

 the largest specimens of G. calcarata, has the tips separated and bifid, 

 the inner spine being slightly longer. 



The first of these characters can not be regarded as of specific value. 

 Dohrn's specimen measured 155 mm., Sars's specimen 157 mm. The 

 largest G. calcarata at hand (and ever observed) measures 115 mm., 

 and consequently, is considerably younger than the known specimens 

 of G. ingens. Now, as shown below, it is a general rule in this genus 

 that all the spines of the carapace and the rostrum decrease in rela- 

 tive size with advancing age, and thus it is easy to believe that the 

 slight development of these spines in G. ingens is due to old age only. 

 In fact, if we imagine that G. calcarata grows larger and that the 

 spines decrease proportionally, we would obtain, at about the size of 150 

 to 160 mm., the conditions found in G. ingens. 



As to the second differential character, the lack' of the two oblique 

 keels on the upper face of the carapace, this may have been over- 

 looked by Dohrn and Sars. In fact, these two keels were overlooked 

 by Sars in G. calcarata; at any rate, they are not mentioned in the 

 description, although one of the figures (Plate IV, fig. 2) shows traces 

 of them. 



The third character offers only a slight difference from the condi- 

 tion seen in large specimens of G. calcarata. In the latter the tips 

 of the epimeral plate of the sixth abdominal segment are in contact in 

 the median line, while in G. ingens they are separated, according to 

 Sars's fig. 6 on Plate II. Moreover, in G. calcarata the outer spine 

 of the bifid end of each of the tips is greatly longer than the inner, 

 while in G. ingens the inner spine is slightly the longer. 



At present this last character remains the only one upon which 

 G. ingens and G. calcarata can be separated, and it is not improbable 

 that further material will demonstrate that one form passes into the 

 other when we consider the changes in the sixth epimeral plate in its 

 development from the young G. calcarata to the old. 



Distribution of G. ingens. — Off the west coast of Africa: " Laos," 

 depth not recorded (Dohrn). Near Aru Island, Arafura Sea (New 

 Guinea), 800 fathoms (Sars). 



