92 Transactions.— Zoology. 
Idoteide and approaches the Tanaide. The legs consist of an anterior 
series of four, and a posterior series of three, and this, according to the 
figures given by Bate and Westwood, appears to be the case with the 
Tanaide. This peculiarity is also possessed by the Amphipoda to which 
Phreatoicus has a considerable superficial resemblance due chiefly to the 
flattened form of the body, best seen in the abdomen, and to the fact 
that the segments of the pleon have the integument produced downwards, 
but also to the Amphipodan facies of the legs and the last pair of pleo- 
poda. 
The precise place of Phreatoicus in any system of classification cannot 
as yet be indicated with certainty, but one thing is made clear by the dis- 
cussion, viz., that Phreatoicus, possessing as it does affinities to several dis- 
tinct groups, must be of very considerable antiquity. 
The occurrence of this species has been somewhat remarkable. Ever 
since January, 1881, I have collected or had collected for me all the 
Crustacea that were observed to come up; nothing new was found until 
the beginning of September, 1882, when a single specimen of Phreatoicus 
was obtained, and in the short time since then six other specimens have 
been found. 
DESCRIPTION OF PLATE IV. 
Phreatoicus typicus. 
Fig. 1. Lateral view of the animal x 5. 
2. Upper antenna x 30; a, auditory cilium from the same, more highly magnified. 
3. Base of lower antenna x 13. 
4. Side view of the head, showing the mouth organs in position, x 15; a, labrum; 
b, mandible with appendage ; c, the two lobes of first maxilla; d, second max- 
illa ; e, maxillipede with f, the rounded plate at its base. 
9. Mandible, view of inner side x 20, 
6. Labrum x 30. 
7. First maxilla x 30. : 
8. Second maxilla x 30; a, seta rom middle lobe of same, more highly magnified 
9. Maxillipede x 30. 
10. Distal portion of first thoracic leg x 30. 
ll. Seventh thoracic leg x 13; a, end of same x 30. 
12. First pair of pleopoda x 13. 
13. Second pair of pleopoda x 15. 
14. Extremity of abdomen, side view, x 14. 
15. Portion of the integument x 120. 
