REPORT ON THE CRUSTACEA MACRTJRA. 363 



The second pair of antennae (c) consists of a basal joint that supports two branches 

 one of which is two-jointed, the first joint being long and cylindrical, the second short, 

 more slender, and tipped with four long hairs ; the other branch is also cylindrical, multi- 

 articulate, and fringed with hairs, one being attached to each articulus on the outer side. 



The labrum is armed with a long tooth or spine directed forwards and reaching 

 beyond the frontal margin. 



The mandibles and oral appendages I have not been able to determine in this unique 

 specimen, but they, as well as the two pairs of gnathopoda, are present. 



The pereiopoda are still in an undeveloped condition, existing as long, narrow, 

 saccular processes. 



The pleopoda are not yet present, except the posterior pair, which consists of a basal 

 joint that supports two subequal membranous branches. 



Length, l - 5 mm. (0'06 in.). 



Habitat. — The Pacific Ocean. 



Aprfl 3, 1875 ; lat. 25° 0' N., long. 137° 50' E.; south of Japan, between Stations 

 229 and 230. 



Platysacus crenatus, 1 n. gen. et sp. (PI. LXIIL). 



This form of Elaphocaris must, I think, belong to a very distinct species, and for the 

 sake of convenience I propose to call it Platysacus crenatus. It differs from all the 

 others in having a series of crenated or small tooth-like points crowning each of the ten 

 lobes which are disposed around the margin of the carapace, and the dorsal surface is 

 covered with eleven long spine-like teeth. 



The rostrum is straight, free from ornamentation, and reaches a little beyond the 

 ophthalmopoda. On each side of the frontal margin, corresponding with the outer 

 canthus of the orbit, is a long spine-like tooth, subequal in length to the rostrum ; 

 posterior and a little external to this, within the margin, and standing on the antennal 

 region, is another long spine-like tooth, and on the outer antennal angle is a broad flat 

 lobe, directed obliquely outwards and upwards, and crowned with nine or ten fine points 

 or teeth. Posteriorly, on the lateral margin, and corresponding with the line of the oral 

 cavity, is another broad flat lobe of extreme tenuity, the margin of which is fringed with 

 a series of ten or twelve fine, sharp, tooth-like points ; within this on the dorsal surface, 

 in a line with the oral organs, are two long and distinct spine-like teeth ; posteriorly, on 

 the lateral margin, are three more broad, flat, delicately thin lobes, crowned with 

 numerous small tooth-like points, varying from six or seven to twelve or more, the 

 posterior standing laterally to the median line of the carapace. In a transverse line 

 corresponding to the anterior portion of the third or middle marginal lobes, there stand 



1 From xXari/f, flat, and car.o;, shield. 



