404 PERCY 8LADEN TRUST EXPEDITION 



16. Lysmatella prima Borradaile, 1915 (Plate 58, fig. 7). 

 Ann. Mag. Nat. Hist. (8), xv. p. 209. 



Diagnosis: The body is compressed, the carapace of a good length, keeled in the 

 forepart and provided with a strong antennal and a small pterygostomian spine. The 

 rostrum is straight at first but gently upcurved towards the tip, outreaches the 

 antennular stalk, and has the formula ^zr^, the first tooth standing detached on the 

 carapace, the ventral teeth smaller than the dorsal, and all the teeth sloping very 

 sharply forwards. The rostrum becomes relatively longer and more strongly curved as 

 the individuals increase in size. The antennule has a long, slender stalk, and the 

 stylocerite short, wide and curv.ed. The antennal scale reaches the end of the penulti- 

 mate joint of the antennular stalk, and is narrow, with nearly parallel sides and a broad, 

 rounded end. The third maxilliped is as stout as the Jirst leg, in which the hand and 

 arm are subequal, the wrist a little shorter than either, and the fingers gape somewhat 

 widely. In the second leg the wrist has 20 — 22 joints, of which the last is longer 

 than any of the others. The dactyles of the ivalking legs are provided, besides the 

 end-claw, with three moveable spines on the lower side, and of these the third is larger 

 than the end-claw. The telson is barely shorter than the uropods, bears two pairs of 

 moveable spines above, and is fringed with long, stout hairs. 



Length of the longest specimen 1 9 mm. 



Specimens were taken in Haddumati, Mulaku, and South Nilandu Atolls, Maldives. 



Family Pal^monid^. 



Subfamily Pal^monin^. 



Genus Leander. 



17. Leander debilis (Dana), 1852. 



Palaemon debilis, Dana, U. S. Explor. Exped. xiii. i. (Crust.), p. 585, PL 38, figs. 6 — 7. 

 de Man, Abb. Senckenb. Ges. xxv. iii. p. 808 (1902). 



The collection contains a large number of specimens of L. debilis from Aldabra 

 which show the great variability which characterizes this species. The rostrum varies 

 in length, shape, and dentation. It may be as long as, shorter than, or longer than 

 the antennal scale. Its curves difier considerably in the specimens. Its formula in 

 these examples is fEf, most commonly ^, including the small tooth which is nearly 

 always present near the tip. The size, shape, and spacing of the teeth varies. The 

 wrist of the second leg varies in length, but usually falls a little short of the end 

 of the antennal scale. The antennule agrees with de Man's description. 



There are also a number of specimens from a "barachois" in Diego Garcia. 

 These are less variable than the Aldabra specimens. The rostral formula is jE|, 

 usually |. The average size is less than that of the Aldabra specimens, the largest 

 specimen measuring 28 mm. in length. It is quite possible that we have here two 

 distinct but closely allied species, such as the L. debilis and L. gardineri found in 



