ii7 



North Balabac Strait, 58 fathoms (" Albatross" Stat. 5356; Cat. N° 35275 U.S. Nat. 

 Mus.); 2 Ex. These have 15 and 21 arms. 



Verde Island Passage, 180 fathoms ("Albatross" Stat. 5367; Cat. N" 36224 U.S. Nat. 

 Mus.); 1 Ex. 



Near Marinduque, 106 fathoms ("Albatross" Stat. 5369; Cat. N ü 35949 U.S. Nat. Mus.); 

 1 Ex. A typical example with 1 2 arms. 



Tawi Tawi group, 12 fathoms ("Albatross" Stat. 5154; Cat. N° 35270 U.S. Nat. Mus.); 

 1 Ex. There are 19 arms. 



Zebu reefs, littoral (from the "Challenger" collection; Cat. N° 17529 U.S. Nat. Mus.); 1 Ex. 



Decametra A. H. Clark. 



Key to the Species of the Genus Decametra. 



a 1 The distal edges of the segments of the much enlarged and stiffened P 2 , which 

 is from half again to twice as long as the approximately equal P T and P 3 and 

 is composed of 14 — 20 segments, bear groups of prominent spines at the 

 prismatic angles; lower pinnules all stiffened; 16 — 20 cirrus segments; arms 



50 mm. long (southern Japan) tigrina 



a 2 The distal edges of the segments of P 2 do not bear groups of prominent spines 

 at the prismatic angles ; except for P 3 and sometimes P., (more rarely Pj) the 

 lower pinnules are not stiffened 



b 1 P 3 resembling P 3 and longer than Pj ; P 2 with 15 — 17 segments 

 c 1 20 — 23 cirrus segments; arms 65 mm. to 75 mm. long 



d 1 cirri stouter, the majority of the segments being twice as broad as 



long or even somewhat broader (Philippine Islands) . . . . mylitta 

 d 2 cirri more slender, the majority of the segments being only slightly 



broader than long (K u r r a c h i , I n d i a) inollis 



c 2 25 — 29 cirrus segments; arms 80 mm. to 1 10 mm. long 



d 1 P„ is stout, less than half again as long as P x , and none of its comp- 

 onent segments are longer than broad (sou th western Indian 



Ocean) alaudae 



d- P„ is rather slender, nearly or quite twice as long as P x , and most of 



its component segments are from half again to twice as long as broad 



e 1 most of the segments of P, are from one third to one half again 



as long as broad, with prominent, though not spinous, distal ends 



(C e y 1 o n) taproöa?ies 



e 2 most of the segments of P 2 are twice as long as broad, with spinous 



distal angles (M uscat,Arabia) arabica 



b 3 P„ shorter than P l 



c 1 P 2 has 17 — 18 smooth segments which do not bear spines on their distal 

 angles; arms 45 mm. to 50 mm. long 



