ISOPOD GENUS LIGIDIUM. 825 



the hin.1 border of the tergite, there is often presenb on its hind 

 e.lge n patch of stifi' bristles arranged in about three transverse 

 rows fonmi.g, as ib were, a thick fence of stakes at the entrance 

 to the litfcle valley. Verhoefl' (1918) has suggested that this 

 i4)parn,tiis may be used as a comb for cleaning the antennro, but 

 coiihrmatory observations have yet to be made. 



The edges of the tergites are beset with " Schuppenborsten " 

 similar to those of Ligia, as described by Wahrberg— that is to 

 say, the bristle usually projects slightly, but never conspicuously 

 from the scale ; it is sometimes not easy to detect. 

 _ The abdomen (metasome) is always abruptly contracted. The 

 hrst two somites are covered by the last thoracic somite, and are 

 without drawn-out pleural plates, but the remaining somites 

 Have these moilerately drawn out. The terminal somite is very 

 similar lu form in all species. The hind border is arcuate or 

 very bluntly angled in the median line ; it is notched above the 

 insertion of the uropods to a greater or less extent in difierent 

 species, but no distinctive angles or spines are developed. 



Appendages. 



The antenna; fantennules) are of three segments, the distal of 

 which is almost vestigial. They always project beyond the front 

 of the head in this genus. Sensory . bristles are found on each 

 segment and n. terminal bunch on the last of a few short stiff 

 rods. ('.L'ext-ng. 2, a.) 



2nd antennae. Five segments and an obscurely segmented 

 (lagelluui of not more than 15 or less than 9 segments, ending in 

 a dense brush of sette. In the subgenus TyjMolhjidmm the 

 tlagellum has 19-23 segments. The number of segments on 

 the flagellum appears to increase in number till fully adult 

 (Text-fig. 2,6.) ^ 



Right mandible. Three strong biting teeth; large lacinia 

 mobilis beset with many strong bristles, but not chitinized ; 

 3 hairy setre between biting teeth and molar tubercle on base 

 of lacinia mobilis. Molar tubercle not high-crowned, and bearing 

 a dense row of setose bristles on its free posterior edge. A 

 bunch of long non-setose bristles between lacinia mobilis and 

 molar tubei-cle. (Text-fig. 1, a & c.) 



Left mandible. Three or four strong biting teeth; lacinia 

 mobilis with 3 chitinized teeth ; 3 or 4 hairy bristles between 

 biting teeth and molar tubercle on base of lacinia mobilis. 

 Molar tubercle high-crowned ; its surface strongly ridged. 

 (Text-fig. 1, 6 &fZ.) t,j t^ 



1st maxilla. Lacinia exterior with 4 large teeth and 3 or 4 

 small ones. Lacinia interior with three very stout hairy bristles, 

 the two inferior of which are equal and larger than the upper- 

 most one. (Text-fig. 1, 0&/.) 



2nd maxilla. Obscurely divided into two lappets, the smaller 

 •on the outer side ; on the inner side are seen two richly setoso 



