BORRADAILE— ON THE PONTONIIN^ 393 



1. (Type.) Conchodytes tridacnce Peters, 1851. 



Gas. naturf. Freunde Berlin, 1851 (Jide Hilgendorf ) ; Ber. k. Ak. Wiss. Berlin, 1852, 

 p. 594; Arch. Naturg. xviii. p. 288 (1852). Hilgendorf, Monatsber. k. Ak. Wiss. Berlin, 

 1878, p. 835. Borradaile, Ann. Mag. Nat. Hist. (7), ii. p. 390 (1898); Proc. Zool. Soc. 

 Lend. 1898, p. 1007 (1899); Willey's Zool. Results, iv. p. 407 (1899). Nobili, Ann. Mus. 

 Genova, xl. p. 235 (1899); Ann. Sci. Nat. (9), iv. p. 66 (1906). 



Pontonia tridacnce, Dana, U.S. Explor. Exped. Rep. xiii. i. p. 371 (1852); Atlas, 

 PL 37, fig. 1 (1885). Miers, "Alert" Rep. Crust, p. 290 (1884). ?Ortmann, Speng. 

 Zool. Jahrb. Syst. v. p. 509, PI. 37, fig. 10 (1891). 



Indopacific, in Tridacna. 



The separation of this species from C. meleagrincB is difficult. Peters, whose state- 

 ments are none too explicit, gives several points of difference, but these all vary 

 independently, with the exception of that which consists in the absence of a fringe 

 to the antennal scale in C. tridacnce. I have not met with this feature, and believe 

 it to have been due to accident in Peters' specimens. Examination of a number of 

 specimens from various localities shows the following facts: (l) specimens in which 

 the rostrum outreaches the antennal scale always have the third maxilliped falling 

 considerably short of the end of the rostrum, and the arm of the first leg no longer 

 than the wrist, and are always found in Tridacna, (2) specimens in which the rostrum 

 is outreached by the antennal scale may have the third maxilliped reaching or ex- 

 ceeding the end of the rostrum, and may have the arm of the first leg longer than the 

 wrist, and are usually, though not always, found in Meleagrina. Form (l) is presumably 

 C. tridacnce, and form (2) C. meleagrince. Whether they are specifically distinct is 

 another question. In both forms the chelipeds of the second pair vary greatly both 

 in degree of inequality and in the actual size of the greater of them. 



2. Conchodytes meleagrince Peters, 1851 (Plate 57, fig. 26). 



Ges. naturf Freunde Berlin, 1851 {Jide Hilgendorf); Ber. k. Ak. Wiss. Berlin, 1852, 

 p. 594; Arch. Naturg. xviii. p. 288 (1852). Hilgendorf, Monatsber. k. Ak. Wiss. Berlin, 

 1878, p. 836. Borradaile, Ann. Mag. Nat. Hist. (7), ii. p. 390 (1898). Nobili, Mem. Ac. 

 Torino (2), Ivii, p. 59 (1907). Pearson, Rep. Ceylon Pearl Fisheries, iv. p. 77 (1905). 



Pontonia meleagrince. Bate, " Challenger" Macrura, p. 707, PI. 124, figs. 1, 2 (1888). 



Pontonia tridacnce, Miers, "Alert" Rep. Crust, p. 290 (1884). 



1 Pontonia maculata, Stimpson, Proc. Ac. Philadelphia, 1860, p. 38. Balss, Abh. 

 k. Bayer. Ak. Wiss., Math.-Phys. Kl. ii. Suppl. Bd. x. p. 53 (1914). 



'i.Pontonie enjlee, H. M. -Edwards, Hist. Nat. Crust, ii. p. 360 (1837). 



Indopacific, in Meleagrina, and occasionally in Tridacna. 



3. Conchodytes domestica (Gibbes), 1850. 



Pontonia domestica, Gibbes, Proc. Am. Assoc, iii. p. 196 (1850). Kingsley, Proc. 

 Ac. Philadelphia, 1878, p. 95. 



Pontoma{^) domestica, Borradaile, Ann. Mag. Nat. Hist. (7), ii. p. 389 (1898). 

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