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216 



STALK-EYED CRUSTACEA. 



In small individuals of this species the rounded lateral expansions of the 



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carapace behind the antennal spines are more prominent and the antennal 

 spines relatively smaller than in full grown specimens. 



G. willemoem was discovered by the naturalists of the " Challenger " Expe- 

 dition in 1874. Two specimens were procured south of Amboina, lat. 4"" 21' 

 a, long. 129^ r E.; depth, 1425 fathoms. 



Branch iostcgal 



Gnathophausia brevispinis Wood Mason, 



Plate J. 



Gnathophausia gracilis^ var. brevispinis Wood-Mason, Ami. Mag. Nat. Hist., Cili Ser., VII. 188, 1891. 

 Gmthophausia brevispinis Wood-Mason, Ann. Mag. Nat. Hist., 6th Scr., VIII. 269, 1891. 

 Gnathophausia dentata Eax., Bull Mus. Comp. ZooL, XXIV. 217, 1893. 



Rostrum somewhat shorter than the remaining part of the carapace, 

 slender, gently up-curved, its three margins armed with teeth, those of the 

 superior margin the largest. At the base of the rostrum, over the anterior 

 part of the gastric region, rises a pi-ominent thin triangular crest, produced 

 at the apex to a spine; there are in most specimens a minute denticle near 

 the anterior, and one to three near the posterior, end of the crest. Supra- 

 orbital spines small, not distinctly defined from the base of the rostrum. 

 Antennal spines of moderate length, slender and acute, 

 spines very long, their bases expanded into wing-like processes on each side 

 of the carapace. Cervical groove distinct. Dorsal keel obsolete on the 

 posterior gastric region, distinct behind the cervical groove and armed with 

 a row of small teeth. Posterior dorsal spine rather short, scarcely projecting 

 beyond the first abdominal somite; it is directed upward at a much stronger 

 angle than is common in this genus. Near the infero-posterior angles of the 

 carapace are two spines, the upper of which is long and slender, equalKng 

 the dorsal spine in length, while the lower one is reduced to a tooth, obsolete 

 in some specimens. The lower lateral keel is distinct, terminating in the 

 upper of the two spines at the infero-posterior angle. Below this another 

 minutely denticulated submarginal keel runs from the branchiostegal spine 

 backward to the lower and smaller spine of the infero-posterior angle of the 

 carapace. The upper lateral keel is obsolete. 



The abdomen is rather slender, and Is armed with a row of seven dorsal 

 spines; two of these occur on the first segment, two on the second, and 

 one on each of the three following segments ; the two spines on the second 

 segment, together with the posterior spine of the first segment, arc much 



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