NO.1480. SCinzoi'uD CRUSTACEANS— ORTMANN. 45 



also intermediate with regard to the character* 1, #, and 3. Younger 

 individuals among the material examined by the writer possess invari- 

 ably the antennal scale of G. zoea, but it must be added that the ser- 

 rations of the outer margin are very fine. I can not see them with 

 the naked eye, and an ordinary magnifying lens scarcely shows traces 

 of them, but stronger instruments reveal them distinctly as sharp points 

 for quite a distance along the margin of the spine. 



c. Young specimens extracted from the marsupium of a typical 

 G. willemoesi have an antennal scale, which, in shape, is that of 

 G. zoea, the marginal spine being longer than ' the lamellar portion. 

 However, I could not ascertain the presence of serrations on the 

 margin. Under the microscope, there is a kind of undulation of the 

 margin, but no sharp, spiniform teeth. But this is not astonishing, 

 since it is in keeping with the fact, that the serrations or denticu- 

 lations of rostrum and postero-dorsal spine are not present in these 

 embryonic individuals, while they are well developed in young specimens 

 after they have left the marsupium. 



d. Similar changes in the length of the spine of the antennal scale, 

 due to age, have been found in another species, G. longispina. 



Thus, I think, the assumption well supported, that the characters 

 given for G. zoea are only such as are due to the immaturity of the 

 specimens, and that those assigned to G. willemoesi belong to the older 

 stages of the same species. The name of G. zoea has the priority 

 over G. willemoesi. 



G. sarsi. — For G. sarsi, the following differences from G. willemoesi 

 are given by Wood-Mason". 



1. The dorsal spine reaches to the posterior end of the third abdom- 

 inal segment. 



2. "Extreme edge (of carapace) expanded at the postero-inferior 

 angle into a conspicuous rectangular lamina, into which neither its 

 lower lateral keel nor its raised rim enters." 



3. Upper half of the posterior margin of the carapace on each side 

 and the lateral edges of the dorsal spine are minutely denticulated. 



4. Five anterior abdominal segments with two subdorsal keels. 



5. The telson is tricarinate, having a fine median carina, and "appears 

 to be more produced at the tip than in any other species." 



The following remarks are to be made: 



1. As I have already shown, the length of the dorsal spine can be 

 disregarded; in the present case, the length agrees well with the size 

 of Wood-Mason's specimen; in the typical 67. zoea, not longer than 

 TO mm., it reaches beyond the fourth abdominal segment or falls short 

 3i it; in G. sarsi (75 mm.) it reaches to the end of the third segment; 

 in one of our specimens, 88 mm. long, it reaches to the middle of the 

 third segment; in another, about 105 mm. long, to the middle of the 



«Ann. Nat. Hist. (6), VII, 1891, p. 187. 



