90 Bulletin Vanderbilt Marine Mitseum, Vol. VI 



The petasma (text, fig. 5) is composed of symmetrical halves, 

 each of which has the ventral margin curved distally, forming an 

 acute hook which curves over the remainder of the tip. Inside this 

 hook, on the inner surface of the petasma membrane, there is a 

 fleshy knob-like process, and beneath it lies the rounded, curved 

 outward margin of the ventral half of this process. The inner sur- 

 face of the petasma is ridged by folds of the membrane and the 

 inner cavity is somewhat tubular. Behind the bases of the fifth 

 pair of legs in the male there is a thickened transverse bar that 

 widens anteriorly into a median plate. Between the bases of the 

 fourth pair of legs there is a median nodule. 



The thelycum is figured by Dr. Alcock. It consists of a pair 

 of semicircular plates placed with their straight margins side 

 by side in the median line ; these margins slightly bent, rim-like. 

 References : Peneus monodon, Fabricius, Entom. Syst. Suppl., 

 1798, p. 408.— Bosc, Hist. Nat. Crust., t. II, 1802, p. 777.— 

 Latreille, Hist. Nat. Crust., t. VI, 1803, p. 249. — Lamarck, 

 Hist. Nat. Anim. sans Vert., t. V, 1818, p. 206. — Desmarest, 

 Consid. Gen. Crust., 1825, p. 225. — Edwards, H. M., Hist. 

 Nat. Crust., t. II, 1837, p. 416.— Krauss, F. Sudafrik. Crust., 

 1843, p. 55.— Stimpson, W., Proc. Acad. Nat. Sci. Phila., 

 vol. XII, 1860, p. 44. — Heller, C, Reise Osterreich. Fregatte 

 "Novara," Crust., Th. II, Abh. Ill, 1865, p. 122.— Bate, 

 Spence, Ann. Mag. Nat. Hist, ser. 5, vol. VIII, 1881, p. 178; 

 Rept. H. M. S. "Challenger," Zool., vol. XXIV, pt. 1, Ma- 

 crura, 1888, p. 250 (part), pt. 2, pi. 24, fig. 1. — Haswell, 

 W. A., Catal. Austral. Crust., 1882, p. 199.— Miers, E. J., 

 Proc. Zool. Soc, 1884, p. 15. — Henderson, J. R., Trans. Linn. 

 Soc. London, Zool., ser. 2, vol. V, 1893, p. 447. — Ortmann, 

 A., in Semon, Zool. Forschungsr. in Austral, u. d. Malay 

 Arch., Bd. VI, 1894, p. 9.— de Man, J. G., Zool. Jahrb. Syst., 

 Bd. X, 1898, p. 677.— DOFLEIN, F., Abh. Bayer. Akad. Mun- 

 chen, Bd. XXI, heft III, 1902, p. 632.— NoBiLi, G., Boll. Mus. 

 Torino, vol. XVIII, no. 452, 1903, p. 1.— Stebbing, T. R. R., 

 Marine Invest. S. African Crust., publ. by Cape of Good Hope 

 Dept. of Agric. at Cape Town, vol. IV, 1908, p. 74. — Alcock, 

 A., Cat. Indian Decap. Crust., pt. Ill, Macrura, fasc. I, 1906, 

 p. 8, pi. 1, figs. 1, la-b. — Pearson, J., Rept. Ceylon Pearl Oys. 

 Fish, of Gulf of Manaar, pt. 4, 1905, p. 69.— Nobili, G., Ann. 

 Mus. Nat. Paris, ser. 9, t. IV, 1906, p. 11. — Doflein, F., Mun- 



