NO. 1480. SCHIZOPOD CRUSTACEANS— ORTMANN. 31 



Antennal scale small, subovate, pointed; point not produced. Outer 

 margin serrate, serrations three to six (sometimes different on right 

 and left sides), the distal serration at a certaiji distance from the tip of 

 the scale, and the margin between this serration and the tip either 

 straight or slightly emarginato, thus giving a more or l(>ss truncate 

 appearance to the scale. 



Abdomen sculptured ])y a distinct transverse groove near the pos- 

 terior margin of each of the live anterior segments; there is a similar 

 but fainter groove near the anterior margin. The posterior groove 

 is continued down to the epimeral lappets, and here its anterior edge 

 is marked on an elevated ridge. This sculpture is seen clearly onl}' in 

 well-preserved specimens, and sometimes there are traces of a sub- 

 dorsal longitudinal keel on each side. Also a l)lunt median keel is 

 sometimes indicated. The epimera of the second to the iifth segment 

 consist of two lappets, which are both produced and acutel}' pointed, 

 the posterior being somewhat longer than the anterior. The anterior 

 lappet of the first segment is considerably shorter than the spiniform 

 posterior lappet, and is not produced into a spine, but bluntly pointed 

 or even obtuse. The epimera of the sixth abdominal segment unite 

 ventrally to form a concave, cordiform plate, which, in old individ- 

 uals, is produced be3'ond the posterior margin of the sixth segment. 

 In 3^oung individuals the right and left lappets are short and simpl}^ 

 pointed, and separated from one another by a shallow emargination. 

 AVith increasing age they become much elongated, are separated bv a 

 narrow slit, and the tips become bitid, a second point developing on 

 the inner side, which is alwaj's much shorter than the outer point. 

 In old individuals the inner tips are in contact in the median line and 

 may even overlap. 



Variations with ar/e. — I had an excellent opportunity to study this 

 species, as over 40 individuals in good condition were available, of 

 very different sizes and ages, ranging from ^'2 nnu. to about 115 mm. 

 The three first-named specific characters are always present, but the 

 fourth is observed only in older individuals. The spines of the cara- 

 pace are vevy variable in their development according to age, and 

 generally they are comparatively longer in young specimens and 

 shorter in old ones. Sometimes, in the cases of the l)ranchiostegal 

 and postero-inferior spines, even the absolute length in older speci- 

 mens is inferior to that in younger ones. This seems to be a general 

 rule in this genus, for it was discovered by the writer in another 

 species of the genus, G. longispina.^ 



Another important variation, due to age, is found in the ventral 

 epimeral plate (see Plate I, figs. 2«-2/). The smallest individual (42 

 mm., Station No. 3627, fig. 2^^) has this plate very short; the two tips 



«Bull. U. S. Fish Comm. for 1903, 1905, p. 970. 



