136 WALTER GARSTANG, M.A. 



II. 



Ascidia depressa, Alder. 



Ascidia depbessa, Alder. Cat. Moll. North. Durham, Trans. Tyneside 

 Nat. Field Club, 1848, p. 107. 



— — non Heller. TJntersucli. iiber die Tunicaten d. 



Adriat. Meeres, Denks. d. Kais. 

 Akad. Wiss. Wien., xxxiv, ii, 1875, 

 p. 15,Taf. v., figs 10—12. 



— — nee Herdman. Notes on British. Tunicata, Journ. 



Linn. Soc, xv., 1881, pp. 286, 287, 

 pi. xviii., figs. 4, 5. 



— — nee Boule. Kech. s. les Ascidies Simples d. Cotes 



de Provence, Ann. Mus. d'Hist. 

 Nat. Marseille, torn, ii, 1881. 



Under this name I describe a species of Ascidian of which I took 

 four specimens on May 11th. They were attached to the under sur- 

 face of a stone near the Zostera bed off Nodes Point. 



Specific Diagnosis. — Body oblong ovate, much depressed, greenish 

 when alive, attached by the whole of the left side. Oral aperture subter- 

 minal ; cloacal two-thirds of the way down, on the right side, near the 

 dorsal edge. Test rather thin, cartilaginous, provided with numerous 

 minute tubercles on its free surface. Oral and cloacal siphons, especially 

 the cloacal, rather long. Stomach rounded, at the posterior end of the 

 body ; first bend of intestine considerably anterior to the cloacal siphon ; 

 rectum directed obliquely forwards, sometimes almost horizontal. Ten- 

 tacles 25 to 30, long and slender. Prcebranchial zone studded with minute 

 papillae. Aperture of dorsal tubercle horse-shoe shaped, horns not in- 

 curved concavity anterior. Ganglion much elongated, slightly dilated at 

 each end. Epipharyngeal groove low, moderately long. Dorsal lamina 

 continued behind the oesophageal opening, fairly deep, strongly ribbed on 

 the convex side and regularly pectinated with stout papillae profusely 

 scattered on the concave side. Pharyngeal wall minutely plicated ; 

 horizontal bars usually broad and narrow alternately, their breadth never 

 exceeding half the length of the meshes; internal longitudinal bars 

 slender ; papilles above the connecting ducts erect, discoid, provided with 

 a supporting ridge in front and behind ; no intermediate papillse ; meshes 

 square, each containing four or five stigmata. (Esophageal aperture on 

 dorsal side of pharynx, near its posterior end. 



The body in all the specimens is much depressed, oblong in form, 



with sloping and expanded edges, and attachment is affected by the 



whole of the left side. The position of the oral and cloacal apertures 



is indicated in fig. 7 (PI. VI.), which represents the largest individual 



of twice the natural size. The cloacal aperture varies slightly in 



