A ST ROSACEA. 



ANTHEADrf. 



THE THUMPLET. 



Aiptasia Conchn. 



Plate V. fig. 3. 



Specific Character. Body smoke-brown ; disk marked with pale blue 

 lines. 



? Actinia biserialis. Forbes, Ann. N. H. Ser. 1. v. 182 ; pi. iii. Johnston, 



Brit. Zooph. Ed. 2. i. 221 ; pi. xxxviii. fig. 1. 

 Cocks, Rep. Cornw. Pol. Soc. 1851, 6; pl.l. 

 fig. 18. 



Anthea Couchii. Ibid. Rep. Cornw. Pol. Soc. 1851, 11 ; pi. ii. fig. 30. 



Aiptasia amacha. Gosse, Annals Nat. Hist. Ser. 3. i. 416. 



GENERAL DESCRIPTION. 



Form. 



Base. Adherent to rocks, readily detached ; dilated, but smaller than 

 the middle of the column. 



Column. Slender just above the base, enlarging upwards, dilating at the 

 summit into a wide hemispheric cup or trumpet-shaped disk ; four or five 

 times higher than wide; the form susceptible of great and rapid changes 

 from irregular distension. Margin formed by the outer row of tentacles. 

 Substance pulpy. Surface minutely corrugated in the ordinary condition, 

 but smooth when fully distended, pierced with loop-holes ; without visible 

 suckers, yet capable of adhesion. 



Disk. Thin and membranous, greatly expanded as a broad concave cup. 

 Outline circular, but lax, and often undulate, or even revolute. Radii 

 strongly marked. 



Tentacles. Arranged in four rows : the first row containing six, set 

 at half radius, remote from each other, and from the second row ; when 

 fully extended, an inch and a-half long ; the other rows diminish gradually, 

 the outermost being about half an inch in length. All, especially those of 

 the first row, very lax, flexuou3, frequently thrown into sinuous curves, 

 perforate with a large terminal aperture. 



Mouth. Lip thin. Throat irregularly furrowed. Stomach-wall occa- 

 sionally protruded. Two gonidia, scarcely rising into tubercles. 



