the Species of Limnoria. 383 



been drawn from the shape of tlie body, the proportions of 

 its different segments, and the presence or absence of tubercles 

 on the dorsal surface of the pleon. 



Limnoria lignorum has been fully described by Harger, 

 Sars (1897, p. 76), and others, and its characters are pretty 

 Avell known. L. antarctica was described in great detail by 

 Pfeffer in 1887, and in the descriptions of L. pfefferi and 

 L. andrewsi special notice has been taken of the characters 

 distinguishing tiie species. Of L. segnis only the short 

 original description has been published, and it will be con- 

 venient to consider its characters here somewhat more fully 

 and with special reference to the points mentioned above. 



Limnoria segnis, Chilton. 



Limnoria segnis, Chilton, 1883, p. 76, pi. ii. %. 1 ; Stebbing, 1904, 

 p. 714. 



General Description and Comparison with other Species. — 

 The general appearance is in close agreement with L. Jig- 

 norum, though the body is usually slightly broader and 

 more convex and looks rather more compact. The whole 

 surface is thickly covered with short seta?, with some longer 

 ones, especially on the margins of the segments. The body 

 is generally of a dull white or cream colour, and does not 

 show the grey markings usually present on L. lignorum. 

 As in that species and in L. pfefferi the head is almost 

 globular and is narrower than the rest of the body ; the first 

 segment of the perseon is longer than any of the succeeding, 

 but 1 have not noticed on it the conspicuous dorsal V-shaped 

 grooving described by Stebbing for L. pfefferi] the side- 

 plates agree generally with those of L. lignorum, and the 

 same is true of the pleon and the terminal segment. 



The fifth segment of the pleon is much longer than any of 

 the four preceding, especially in the median line, and in 

 dorsal view it shows the shape as drawn by Pfeffer for 

 L. antarctica ; it bears a faint median ridge. On the last 

 segment, near its anterior margin, there is a slight median 

 elevation or tubercle, from which extend posteriorly two faint 

 parallel ridges. These markings are visible only in speci- 

 mens that have been dried, and even then, owing to the short 

 setfe covering the general surface of the body and the 

 extraneous matter entangled in them, they are not always 

 very distinct, esjiccially in smaller specimens; the}' arc, 

 however, interesting as showing some approach to the 

 tubercles and ridges described by Miss Richardson in 



I 



