igil] ASCIDIANS FROM THE COASTS OF CANADA. I35 



Genus, Tethyum (sens, nov.) 



Syn. Cynthia, Halocynthia, Pyura auci. part., non Tethyum Hart- 

 meyer, 1909. 



Oral aperture terminal, atrial on dorsal side. Siphonal spinules 

 acicular. Surface with simple or branched spines. 



Aperture of dorsal tubercle curved, usually forming two cone-shaped 

 coils; opening between horns directed forwards and to left. Dorsal 

 groove with languets. Number of folds variable, increasing with age, 

 at least 6, the second not smaller than the first and third. Stigmata 

 longitudinal. 



Two to many gonads on each side, those of the left side placed across 

 the inner side of the intestinal loop (which is transverse to the long axis of 

 the body). The two genital ducts open at the anterior end of each gonad. 

 The gonads of each side are fused together posteriorly. The testicular 

 lobes are grouped around the posterior ends of the ovaries. 



Type species — T. papillosum Gunner. 



Hartmeyer (Zool. Ann., Bd. Ill, 1908) has indicated Ascidia rustica 

 L. and A. quadridentata L, as the types of Tethyum Bohadsch. He 

 seems, however, not to have considered Art. 30 of the International 

 Rules, in which we find the following: 



"(e) The following species are excluded from consideration in se- 

 lecting the types of genera. 



(a) Species which were not included under the generic name at the 

 time of its original publication." 



It is possible that he may interpret this to mean only those species 

 that have been named binominally. In that case he would neglect the 

 four species of Bohadsch. Following Sherborn, he has accepted the 

 species of Gunner as validly named. Gunner (Trond. Selsk. Skrift., 

 Ill) names three species which are identical with three of the species 

 described by Bohadsch. Hartmeyer states that Gunner's article ap- 

 peared in the same year as the 12th edition of Linne's Systema Naturae 

 (1767), and considers that Linne's work has the priority. He has evi- 

 dently not seen the original article by Gunner, which (according to Sher- 

 born and Hopkinson) appeared in 1765, but only the German translation 

 (Dront. Gess. Schrift., III). That it antedates Linnaeus is shown by a 

 reference of the latter under A. intestinalis, viz. "Act. nidros. 3. p. 81, 

 t.3. .3, 4. Tethyum." This refers to Gunner's description and figures 

 of Tethyum sociahile. 



As Hartmeyer has not indicated a type from among the species 

 originally included in the genus — either practically (those of Bohadsch) 

 or binominally (those of Gunner) — a type remains to be indicated. Of 

 the species of Bohadsch, the one which we can identify to-day with the 



