178 The Philippine Journal of Science 1915 



pendages are sprinkled with large, black chromatophores. The 

 carapace is similarly pigmented, the pigment spots toward the 

 posterior end showing a tendency toward aggregation into a 

 transverse band. Each of the last 3 thoracic and first 5 abdom- 

 inal somites bears a narrow posterior band, which in the case of 

 the abdominal somites is sometimes interrupted in the middle. 

 In the median portion of each somite there are also 2 other 

 narrow bands of pigment, distinctly separated in the middle, 

 but always joined laterally. There are thus in this species 3 

 distinct bands on each somite in place of the 1 or 2 found in 

 allied forms. On the sixth abdominal somite there is a single 

 large, round, dusky patch on either side. On the telson, much as 

 in L. multifasciata, a patch of black pigment invests the bases 

 of the 2 outermost pairs of the dorsal series of teeth; the base 

 of the median tooth is pale, and there is also a pale intrusion 

 between the first and second lateral teeth. The uropods are 

 suffused with black pigment at the proximal end of the basal 

 segment, on the endopod, and on the joint between the 2 segments 

 composing the exopod. 



Lysiosquilla vidua is very closely allied to L. digueti Coutiere, 

 from Lower California, and these 2 species may be distinguished 

 from all other members of the genus by the possession of a 

 trispinous rostrum. 



Judging from Coutiere's account ' of the American species, the 

 two forms may be separated as follows : 



Lysiosquilla vicina Nobili. Lysiosquilla digueti Coutiere. 



Raptorial claw furnished with 10 or Raptorial claw furnished with 8 



11 teeth. teeth. 



Telson with 6 to 8 pairs of subme- Telson with 3 pairs of submedian 



dian denticles. denticles. 



No eyespots on fifth abdominal so- A pair of very prominent black spots, 

 mite or telson. pale in the center and circum- 



scribed by a pale band on fifth 

 abdominal somite, and a pair of 

 similar spots partially fused on 

 telson. 



Lysiosquilla digueti, like L. vicina, inhabits burrows made by 

 Balanoglossus, and the only specimen known was found living 

 commensally with a large polynoid worm in the tubular cavity 

 formed by the genital ridges of the Balanoglossus. The stoma- 

 topod was found in this curious situation fixed to the back of the 

 polynoid. The two commensals resembled one another closely 

 in color, the conspicuous patches of pigment on the Lysiosquilla 



'Coutiere, Bull. Soc. philomath., Paris (9) (1905), 7, 174. 



