214 OSCANIUS. 



3, 3a (shell). MONTEROSATO, Nuova Kivista Conch. Med., p. 48. 

 Susania testudinaria Cantr., MONTEROSATO, Nom. Gen. e Spec. 

 Conch. Med., p. 149. Oscanius tuberculatus Delle Chiaje, VAYS- 

 SIERE, Rech. Moll. Opistobr., Tectibranches, p. 125, pi. 5, figs. 113- 

 121 (anatomy). 



This is the largest species of the genus, attaining a length of 16 to 

 19 centimeters. The shell is more oblong and more swollen than in 

 other species of Pleurobranchus, and is, in proportion to the size of 

 the animal, much smaller. 



The specific nomenclature is unusually involved, but the name 

 proposed by Cantraine seems to be the earliest having a clear title 

 to acceptation. 



O. TUBERCULATUS Meckel. PI. 51, figs. 50 to 57. 



Body oblong, the general tint ochrey red. Mantle not very 

 thick, with irregularly scattered, unequal tubercles, which are never 

 nearly so large as in 0. testudinarius ; mantle rounded, emargiuate 

 in front, dark red with light spots, not as large as the foot. Foot 

 voluminous, projecting all around the mantle, with a deep sinus in 

 front, and a gland on the posterior median part of the sole. Gill 

 covered by the mantle, folded longitudinally, quite long, with 23-34 

 alternating pinnules on each side of the tuberculate rachis. Anus 

 behind the insertion of gill. Genital orifices and renal pore in 

 front of it ; penis provided with two large triangular membranes. 



Length 12, width 11 centimeters. 



Jaws with the appearance of being carved, composed of small 

 chitinous pieces, each terminating in a denticle, on each side of 

 which there is one, sometimes two, smaller denticles. Radula with 

 the formula 80.0.80, the inner 25 teeth having an external denticle 

 below the terminal hook, which disappears on the outer teeth. 



Shell very large, occupying the greater part of the length of the 

 mantle, quite convex, membranous, with growth lines, and of an 

 iridescent vinous-red color ; length of large shells 43, width 29 mill.,, 

 or, in ordinary specimens, 25 to 30 by 13 to 15 mill. 



Mediterranean Sea : Gulf of Marseilles, in 30 to 70 meters (Vays- 

 siere) ; Algiers (Joly & Monts.) ; Naples (Tiberi) ; Adriatic Sea at 

 Trieste (Stossich) ; Atlantic Coast of France; Southern England and 

 Ireland. Laminarian and Coralline zones. 



Pleurobranchus tuberculatus MECKEL, Beytriige zur vergleichen- 

 den Anatomic, i, pp. 33, 26, pi. 38, f. 33-37, 40 (1808). PHILIPPI, 



