390 PERCY SLADEN TRUST EXPEDITION 



2. Rostrum broad at base. Old World and Atlantic. 



a. Antennal stalk as long as antennular. Eyes and first joint of antennular 



stalk subequal. Japanese. 



P. nipponensis de Haan, 1850. 



b. Antennal stalk shorter than antennular. First joint of antennular stalk 



distinctly longer than eyes. Western species. 



i. Antennal scale has a spine and outreaches antennular stalk. 

 Mediterranean. 



a. Third maxilliped does not reach end of antennular stalk. Body 

 bears yellow spots. 



P. Jlavomaculata Heller, 1864. 



yS. Third maxilliped reaches end of antennular stalk. Body rose-pink. 

 P. tyrrhena (Petagna). 



ii. Antennal scale has no spine and does not outreach antennular stalk 

 W. Indies. 



P. grayi Rathbun, 1901. 



II. Rostrum short, not reaching end of first joint of antennule. 



A. Rostrum reaches middle of first joint of antennule. 



1. Rostrum without keel below. 



P. ascidicola Borradaile, 1898. 



2. Rostrum with keel below. 



P. mexicana Guerin, 1856. 



B. Rostrum not more than -^ length of first joint of antennule. 



P. brevirostris Miers, 1884. 



1. (Type.) Pontonia tyrrhena (Petagna) (Plate 57, fig. 29). 



Astacus tyrrhenus, Petagna, Ent. PI. 5, fig. 5 {fide Risso). 



Gnathophyllum tyrrhenus, Desmarest, Consid. sur las Crust, p. 229. 



Alpheus pinnophylax, Otto, Mem. Ac. cur. nat. Bonn, xiv. PL 21, figs. 1, 2. 



Pontonia tyrrhena, Latreille, Encycl. PL 326, fig. 10 ; Cuvier's R. An. 2nd ed. 

 p. 96 (1829). H. M.-Edwards, Crust, ii. PL 360 (18.37). Cuvier's R. An. Crust. Atlas, 

 PL 52, fig. 4 (1849). Heller, Crust. slidL Eur. p. 251, PL 8, figs. 10, II (1863). 

 Ortmann, Speng. Zool. Jahrb. Syst. v. p. 509, PL 27, fig. 9 (1891). Nobili, Bull. Sci. Fr. 

 Belg. xl. p. 49 (1906). 



Callianassa thyrrhenus, Risso, Hist. Nat. Eur. M^r. p. 54 (1826). 



Pontonia custos, Guerin, Exped. Mor^e, Zool. p. 36, PL 37, fig. 1. Cams, Prodr. 

 Faun. Medit. p. 475 (1885). Borradaile, Ann. Mag. Nat. Hist. (7), iL p. 388 (1898). 



1 Pontonia parasitica, Roux, Mem. sur les Salicoques, p. 26 (1831). 



Mediterranean. In lamellibranchs and sponges. 



