A FOSSIL ISOPOD OP THE FRESHWATER GENUS PHREATOICUS. 



373 



18 mm. The segments of the peraeon that are represented 

 are very distinct, and have a depth of about 3 mm., while 

 the greatest depth of the pleon segments, which are also 

 pretty distinctly shown, is 5 mm. The peraeopoda are not 

 very well preserved, but the portions of them that are 

 present correspond with those already described for speci- 

 mens 1 and 2 ; the three terminal joints of the 6th peraeopod 

 are very distinctly marked, and there are portions of the 

 7th peraeopod extending back about as far as the third 

 segment of the pleon, the extremity being imperfect. In 

 the pleon the first four segments are very well preserved* 

 showing the downward prolongation of the pleural portion 

 very distinctly; that of the second segment reaches further 

 downwards than the first, and is slightly narrower than 

 the third, which is about equal to the fourth. Of the fifth 

 only the anterior portion is present. The terminal portion 

 of the pleon is unfortunately missing in this specimen also. 



Specimen 4, Fig. 4. (Block 233). 



mm 



o ?& 



\ 



^ 



X 5. 



Fig. 4. Phreatoicus wianamattensis, (No. 233). 



On this block, which is brown in colour, much paler than 

 those bearing specimens 1, 2 and 3, the impression shows 

 approximately the same parts as those of other specimens, 

 that is, the posterior segments of the peraeon and the 

 anterior segments of the pleon; but here, apparently, the 



