RELATIONSHIPS OF THE FIXED AND FREE TUNICATA. 179 



many errors may be patent to zoologists, better conversant with the Tunicata 

 than myself. Such, indeed, can only be expected to occur in thus dealing with 

 so comprehensive a subject. I believe, nevertheless, that our acquisitions, as well 

 as those things which are yet desiderata in the interesting study before us, are 

 made much plainer in an attempt of this kind, however imperfect, than perhaps 

 in any other way. The following genera may require brief comment in reference 

 to their zoological characters, and the position assigned to them in the Table : — 



Chelyosoma. 



The absence of branchial tentacula in this genus, and what has been already 

 said of it, p. 171, suggests a position for it near Pelonaia. 



Peroides (mihi). 



Peroides is an Australian genus discovered by me on the Bellona reefs, lat. 21. 51. 

 S., long. 159. 28. E., but as I have given an account of it, with figures, to the Lin- 

 nean Society, I need only allude to its leading features, which are these, — animal 

 recumbent on the left side ; apertures simple on the same plane, and protected 

 by a D-shaped operculum, composed of an indurated fold of the test common 

 to both. 



Cynthia, Ccesira and Molgula. 



The term genus was received by the earlier zoologists in a much wider 

 sense than that to which we now confine it ; and, as might be expected, this has 

 since given rise to much confusion, requiring considerable research to clear up satis- 

 factorily. Thus, under the head of Cynthia, several distinct genera were included 

 by Savigny, and we consequently find that the restricted genus, as understood 

 by Professor Forbes, is represented as having a " circle of tentacular filaments," 

 i.e., simple tentacula; whereas Dr Fleming gives Cynthia the character of " Ten- 

 tacula compound," which could only be applied to a very different genus. It is 

 also remarkable that without any reference to Professor Forbes' s genus Molgula, 

 in a paper read before the Linnean Society and published in the Transactions, I 

 described two Australian Ascidians accurately conformable to Savigny's genus 

 Ccesira, and which, singularly enough, very closely represent the two British 

 species of Molgula described by Professor Forbes ; and my impression has ever 

 since been, that Ccesira and Molgula are synonyms of one and the same genus. 

 Knowing, however, the great and respected authority which this view calls into 

 question, I cannot be positive on the subject, but merely direct attention to it in 

 the hope of setting it right. 



CJiondrostachys (mihi). 

 This name I have given to a very beautiful social Ascidian, which I first 



VOL. XXIII PART II. 3 D 



