112 TETHYS. 



the length of the animal, in an individual 18 lines long, the shell 

 measures 8x6 lines. Penis stouter. 



Differs from A. radiata mainly in the greater size of the shell 

 compared to length of body. It is from the southern part of the 

 Red Sea. 



VIII. Species of unknown locality. 



T. TRIGONA Sowerby. PI. 20, fig. 42. 



Shell small, horny, brown, subtrigonal, ventricose, apex rather 

 straight, acuminately produced, upper margin straight, reflected, 

 obtusely angular at the end ; outer lip straight, obliquely produced 

 before ; dorsal margin obliquely sloped towards the lower margin,, 

 lower margin short. (Sowb.*). 



Habitat unknown. 



A. trigona Sows., Conch. Icon., pi. 4, f. 11 (Aug., 1869). 



This species resembles Aplysia punctata in color, texture, and 

 convexity, but differs from them in its triangular form. 



T. ANGUILLA Cuming. PL 43, fig. 28. 



Shell small, tumid, strongly arched, transverse, pale horn ; apex 

 rounded, small, incurved ; upper margin very short, deeply excava- 

 ted, acuminated at the end ; outer lip obliquely produced ; dorsal 

 margin round ; lower margin oblique, widely excavated. (Sowb.). 



Habitat unknown* 



A. anguilla Cuming MS., SOWB., Conch. Icon., pi. 6,f. 22. 

 A species with very convex shell. 



Unrecognized and spurious species. 



Laplisia viridis Bosc, 1802, Hist. Nat. Vers, i, p. 64, pi. 2, f. 4 

 '(see also Nouv. Diet. d'Hist. Nat., pi. 5, f. 23, and Rang, p. 73), de- 

 scribed from the harbor of Charleston, S. C., belongs, in my opin- 

 ion, to the nudibranch family Elysiidce. 



Aplysia sicula Swainson, Treatise on Malacology, or Shells and 

 Shell-fish, p. 247, fig. 45, (1840). This Sicilian species drawn in 

 outline from life, is entirely unrecognizable from Swainson's sketch,, 

 by which alone it is known. 



Aplysia unicolor Risso, Journ. de Physique, etc., Ixxxvii, p. 374. 



