A REVISION OF THE BEANCHIOSTOMIDiE. 807 



the oral sphincter (iiitra-buccal cirrhi), and this I have not 

 determined in every species. Possibly other more skilful 

 observers may be able to render some of the structures exa- 

 mined by me available for specific and generic characterisation, 

 but my own attempts to make use of the position of the atrio- 

 coelomic funnels, of the skeleton of the prfeoral cirrhi, of the 

 form of the branchial bars (in section), and of the disposition 

 of Miiller^s renal papillae, were unsuccessful. 



The drawings given of B. Belcheri, Bassanum, cali- 

 forniense, and caribseum are the first which have been 

 published of those species. 



The Branchiostomidae are the sole family of known forms 

 comprised in the branch Cephalochorda of the phylum Ver- 

 tebrata. Retaining the name Vertebrata for the great phylum 

 to which some recent writers have proposed to apply the name 

 Chordata, Professor Lankester recognises three distinct 

 branches or lines of descent within that phylum, for which in 

 1877 (J Quart. Journ. Micr. Sci.,' vol. xxvii, p. 450) ^he proposed 

 the names Urochorda (the Tunicates), Cephalochorda, and 

 Craniata. To these three diverging branches Bateson has pro- 

 posed to add a fourth, the Hemichorda, to comprise the forms 

 known as Balanoglossus. We may begin the systematic cha- 

 racterisation of the Branchiostomidae by a definition of the 

 Cephalochorda. 



Branch CEPHALOCHORDA, Lankester, 1877. 



Leptocakdii, Miiller. 'Abhaiidl. k. Akad. Urss.,' Berlin, 1844, 



p. 204. 

 Mtelozoa, J. Geoff. St.-Hilaire. 1852. 

 AcRANiA, Haeckel. ' Gen. Morphol.,' 1866. 

 CiKRHOSTOMi, -^ r ' Lectures on Compar. Anatomy,' 



PHARyNGOBRANCHII, j ^^^' (. 1846. 



Entomocrania, Huxley. 'Proc. Zool. Soc.,' London, 1876, p. 58. 

 Cephalochorda, Hatchett Jackson. 'Forms of Animal Life/ 



1888, p. 437. 



Vertebrata exhibiting the distinctive vertebrate combination 



