500 RADIATA. ACALEPHA. Velella. 



Gen. XIX. VELELLA. — Body gelatinous, with an oblique- 

 ly inserted prominent dorsal crest ; oral disc flat. 



52. V. limbosa. — Body oval, blue ; oral disc with numerous 

 short white filiform tentacula, those of the margin long, une- 

 qual, filiform. 



Holothuria spiralis, Forskael, Desc. On. 104 — V. lim. Lamarck, Hist. ii. 

 482 — Barnstaple, Dr Leach. 



Body attenuating dorsally, bluish ; the crest is suborbicular, compressed, 

 veined ; the oral tentacula are thickest in the middle. An imperfect example 

 of a Velella, which Dr Leach considered as the limbosa of Lamarck, was oblig- 

 ingly communicated many years ago. 



53. V. pociUum. — Body round, white, with a broad striated 



bluish border ; oral disc with unequal clavated blue tentacula ; 



the margin crenulated. 



Medusa pocillum, Mont. Linn. Trans, xi. 201. t. xiv. f. 4.— Coast of 

 Devon. 



Body campanulate; crest subovate, striated, compressed, and extremely 

 thin ; there are about 10 large clavated tentactila, and many intermediate 

 smaller ones. 



Dr Walker, in his MS. adversaria for 1771 states the Medusa velella of Lin- 

 nseus, as having been found at Ose in Sky ; and Mr Pennant in Lis " Caledo- 

 nian Zoology," prefixed to Lightfoot's " Flora Scotica," vol. i. 66. notices 

 the same animal without any remark. It is impossible to determine with 

 certainty to which of the modern species these references belong. 



Gen. XX. EULIMENA. — Body pouch-like, the mouth large, 

 with a simple margin. 



54. E. quadrangular is. — Lengthened, subquadrangular, the 

 oral extremity truncated, the opposite end rounded. 



Flem. Edin. Phil. Journ. viii. 302.— Pentland Frith. 



Length about an inch, breadth half an inch ; transparent; 8 minute ciliat- 

 ed ribs from the crown to the margin ; the oral disc smooth, having the 

 mouth in the form of a transverse slit, leading into an apparently simple 

 central cavity. When active, the cilise are in constant motion, and the body 

 frequently assumes the form of a quadrangular prism. 



Gen. XXI. GERYONIA. — Hemispherical, margin with ten- 

 tacula, the mouth central. 



55. G. equorca. — Orbicular, depressed, with a villous inflected 



margin, bearing tentacula. 



Medusa eq. Mull. Prod. 233. Jameson, Wern. Mem. i. 558 — North of 

 Scotland. 



56. G. hemisphwrica. — With four transverse ribs, enlarged 

 towards the circumference.. 



