18 BOTRYLLIDyE. 



6. L. PUNCTATUM, Forbes. 



A thin, shining, translucent crust, investing stones at low 

 water. The animals, minute, are placed in pairs, each individual 

 marked with a conspicuous black spot. 



Isle of Man, E. F. Cullercoats, Mr. Alder. 



DISTOMA, Gaertner. 



This genus, which is one of the two genera of Compound 

 Ascidians distinguished by Gaertner, belongs to the uni- 

 stellated section of the group styled by Milne-Edwards 

 '• Didemnians." 



The common body, or mass, of Distoma is sessile, semi- 

 cartilaginous, polymorphous, and composed of many sys- 

 tems, usually circular. The individual animals are placed 

 in one or two ranks, at unequal distances from a common 

 centre. They present the striking and distinctive cha- 

 racter of having both branchial and anal orifices regularly 

 and equally six-rayed. The species inhabit the European 

 seas. 



1. D. RUBRUM, Savigny. 



Mem. 2nd part, p. 177, pi. 3, fig. 1, and pi. 13. 



Plate A, fig. 6, and plate B, fig. 6. 



" Mass compressed ; various shades of red, with slightly-promi- 

 nent, oval, yellowish points (individuals) scattered on the two 

 sides, and grouped in systems of from three to twelve. Orifices 

 obtusely rayed, tinted with purple. 



" Mass four to five inches across, and half an inch thick. In- 

 dividuals, two lines." — Savigny. 



This species was communicated to Savigny by Dr. Leach. To 

 it the French naturalist referred the " Alcyouium rubrum, pul- 

 posum, conicum plerumque " of Plancus. (Conch. Min. Not. t. 10, 

 £ B. d.) Mr. W. Thompson has recorded it as occurring on Lami- 

 naria digitata in Belfast Bay, where it was found by Mr. Getty. 

 He remai'ks that the specimens are not so lively in colour as those 

 figured by Savigny. (Ann. Nat. Ilist. vol. v. p. 95.) 



