8 W. A. HERDMAN. 



numerous on the folds than in the interspaces (fig. 5). On the third fold, for example, 

 there are about twenty-three on the fold and seven in the adjoining interspace. In 

 another case, however, there were ten on a fold and five in the interspace. Transverse 

 vessels are of four sizes, of which the three larger sizes (fig. 6, tr, tr', tr") are arranged 

 with regularity (1 3 2 3 1, etc.), and the fourth or smallest size occur irregularly 

 and may be as numerous as four or five between any two of the others. The meshes 

 are elongated horizontally and contain nine to twelve stigmata. The stigmata are 

 rather long and straight, and usually narrower than the interstigrnatic vessels (fig. 6). 



Dorsal Lamina represented by a series of languets, which are smaller and very 

 closely placed anteriorly, and are further apart and larger posteriorly (fig. 4, d. I). 



Tentacles about sixteen, large, of two orders, alternating with a third order of 

 much smaller ones, so : 1 3 2 3 1. 



Dorsal Tubercle very large, about 3x5 mm., horseshoe-shaped, opening anterior, 

 horns turned inwards and coiled (fig. 4). Peri-tubercular area very wide. 



Nerve-ganglion long and narrow, may be over 9 mm. in length, giving off two 

 nerves at each end, which can be traced some way round the sphincters. 



Alimentary Canal forming a very long straight loop. (Esophageal opening 

 large, crescentic, with corrugated lips. Stomach having the wall folded into thin 

 lamellae projecting into the lumen. Anus with laminated edge, attached to the mantle 

 exactly alongside of oesophagus. 



Gonads an elongated compact mass on each side of body, with papillary openings 

 into the atrial cavity. The left gonad entirely fills the intestinal loop. 



This species, which would doubtless fall into the genus Pyura in the nomenclature 

 of MM. Hartmeyer and Michaelsen, was first described by Prof. Sluiter in 1905,* and 

 more fully in 1906,f in his report on the Tunicata of Dr. Jean Charcot's Antarctic 

 expedition of 1903-05. That expedition obtained two specimens of this species at 

 " He Booth Wandel, 40 metres " ; but the figure of the exterior (Exped. Charcot, 

 Plate V., fig. 57) is so formal, and the spines, as represented, are so formless compared 

 with those constituting the most conspicuous feature of the ' Discovery ' specimens, 

 that I failed at first to recognise that I was dealing with the same species. 

 Consequently I drew up the above detailed diagnosis and prepared the accompanying 

 figures (Plate II.), before establishing the identity of my specimens with Sluiter's 

 species. As Dr. Sluiter's lithographer has scarcely done justice to his subject, and as, 

 moreover, there are some points of difference in detail between the figures of the 

 ' Charcot ' specimens and ours, I believe it will be useful to science that this present 

 account of the ' Discovery ' specimens should be published as a supplementary 

 description of the species. 



I would point out : that Plate II., fig. 1, gives a much more life-like 



* Bull. Mus. Nat. Hist. Paris, xi. (1905), p. 473. 



t Exped. Antarct. Franc. (Charcot). Tuniciers, p. 40. [No date. ED.] 



