28 THE VOYAGE OF H.M.S. CHALLENGER 



Patella tramoserica, Lamarck, Anim. s. vert. (ed. Desh.), vol. vii. p. 542, sp. 47. 

 „ „ Eeeve, Conch. Icon., vol. viii. pi. xiii. fig. 27. 



„ „ Angas, Proc. Zool. Soc. Lond., 1867, p. 221, No. 222. 



May 1874. Port Jackson, Sydney. 6 to 7 fathoms. 



Habitat. — Australia, Port Jackson, Sydney (British Museum, Angas). 



2. Acmcea, Eschscholtz, 1830. 



Species. 



1. Acma>a dorsuosa (Gould). 2. Acmma saccharina (Linne). 



3. Acmma virginea (Miiller). 



In regard to the name of this genus, the evidence adduced by Mr Dall is on the whole in favour 

 of Acmcea, Esch., as against Tectum, Audouin and Milne-Edwards. The difficulty, however, of decid- 

 ing between these two names and the want of agreement still prevailing may justify my restating 

 the case in so far as I have personally ascertained the facts. 



No discussion need, I think, be raised regarding the mere words Acmcea or Tectura, nor 

 regarding the diagnosis of the genera supplied by their respective authors. Acmcea is an adjective, 

 but Linne's law says merely, "Nomina generica adjectiva substantivis pejora sunt adeoque non 

 optima." Acmea (sic) had been previously proposed by Hartmann in 1821 for the genus now 

 known by Risso's later name of Truncatella, but was abandoned by its own author in that very year, and 

 may the more freely be set aside, since the same author's genus Acme, also proposed in 1821, has 

 been accepted for a well-known land mollusc. That Eschscholtz in his later diagnosis erroneously 

 puts the branchial cavity on the left instead of the right of the animal is obviously a mere slip of the 

 pen. And, finally, if he did not single out one species in particular as a type of the genus he men- 

 tions, what for his purpose was still better, and is true, namely, that all the species of supposed 

 Patellas found on the north-west coast of America belong to the genus Acm&a. 



On the other hand, " Tecture " is the Gallicised form which French writers always used for Latin 

 names, and the characteristic feature of the genus is distinctly stated by Audouin and Milne-Edwards, 

 and Tectura virginea, Mull., though not named, is plainly referred to as their type species. Further, 

 these authors (men of experience in such matters) certainly believed they had sufficiently determined 

 their genus, for in their finished work (Animaux s. vert, des Cotes de la France, 2 vols. 8vo, Paris, 

 1832, see vol. i. p. 144, note), from which their memoir to the Academy was an extract, they say, 

 referring to their observations on Tectura : " Nous avons pris date pour ce fait . . . dans le resume" 

 des nouveaux recherches sur l'histoire naturelle des cotes de la Manche que nous avons presente a 

 l'Acadcmie des Sciences dans la seance du 26 Octr. 1829." 



I have referred to these points because weight has been laid on them by the advocates of one 

 or other name. But putting aside all these initial questions, we have simply to ask which name, 

 Acmcea or Tectura, has priority of publication. Now as regards that question, had the British Associa- 

 tion accepted the date at which a paper was openly read to a society as the date of publication, 

 no difficulty would have existed, but as the matter stands certainty is impossible. Audouin and 



