REPORT ON THE TUNICATA. 149 



Heller in 1877, 1 distinguished Potycarpa from Styela, on account of the condition of 

 the intestinal loop, and of the genital glands. This separation has not been accepted by 

 Traustedt, but, although Styela and Potycarpa are undoubtedly very closely allied, I find 

 it convenient, on account of the large number of species in both genera, to recognise the 

 distinction until some species turns up which unites the characters of the two groups, and 

 cannot therefore be placed in either. Consequently, with the addition of the new genus 

 Baihyoncus, discovered by the Challenger expedition, I recognise four genera in the 

 Styelinse, and distinguish them briefly as follows : — 



Styelix^e. 



Branchial sac normal. Branchial sac with no stigmata 



in the meshes. 



Xo folds in the branchial sac. Branchial sac folded. Bathyoncus. 



I . 

 Pelonaia. 



! I 



Genitalia as simple Genitalia in the form of numerous 



or lobed tubes. small bodies. 



! I 



Styela. Potycarpa. 



Styela, Macleay. 



Ascidia, Linnaeus, Sys. Nat., Edn. 12. 1766. In part. 



Astidia, 0. F. Muller, Zool. Dan. Prod. 1776. In part. 



Cynthia, Savigny, Mem. sur les Anim. sans Vert l't. ii. fasc. 1. 1S16. In part. 



Styela, Macleay, Anat. Obserr. on the Tunicata. 1823. 



Pandocia, Fleming, British Animals. 1828. 



Cynthia, van Beneden, Eecherches sur les Ascidies. 1846. In part. 



Cynthia, Forbes and Hanley, Brit. Moll., vol. i. 1853. In part. 



Styela, Hancock, Anat. and Phys. of Tunicata, Journ. Linn. Soc. 1868. In part. 



Cynthia, Kupffer, Jahresber. der Commiss., &c. 1875. In part. 



Styela, Heller, Untersuchuugen ii. d. Tun. d. adriat. Meeres., Abth. 3. 1877. 



Styela, Traustedt, ( Iversigt ever de fra Danmark, &<■., Aseidise Simplices. 18S0. In part 



Body attached, sessile or almost so, rarely incrusted with sand. Branchial and 



atrial apertures either four-lobed or cross-slit 

 Test usually thin but leathery, rarely thick and cartilaginous. 

 Bronchial Soc with four or less than four folds upon each side. 

 Tentacles always simple. 

 Intestine forming a narrow loop 

 Genitalia in the form of one or more simple, lobed, or branched tubular bodies 



1 Untersuchungen ii. d. Tunicaten d. adriat. Meeri a., Abth. :;. p. 19. 



