L. Agassiz on the Echinodtrmata, 297 



animals of which Ph. Cookii forms part, which he rejects because it 

 is believed to be the native name of an animal not comprehended in 

 that group. If all generic names (whether classical or barbarous) 

 in the same predicament were to be rejected, how many new names 

 would it not be necessary to introduce into the science in place of 

 those given by the highest authorities ! The other question has re- 

 ference to my Halmaturus Tasmanei ; and as Mr. Ogilby admits it is 

 merely one of precedence, I leave it therefore on his own statement 

 to the decision of those whom it may concern ; observing only, that 

 " previously" can in no way apply to the 28th of February in refer- 

 ence to the 10th of the same month in the same year, or to the 1st 

 of May in reference to the 1st of April. 



I regret to have been placed under the necessity of occupying so 

 much of your valuable space on questions of little more than per- 

 sonal importance. I trust, however, that I have treated them without 

 any exhibition of personal feeling, and it would give me sincere plea- 

 sure to find them met in a similar spirit. 



Yours most sincerely, 



John Edward Gray. 



British Museum, 10th May, 1838. 



XXXIV. — Prodromus of a Monograph of the Radiata and 

 Echinodermata. By Louis Agassiz, D.M.* 



[Continued from p. 43.] 

 I. 

 The order Fistulides or the Holothurise contains but one family, which 

 corresponds to the genus Holothuria of Linnaeus, with the exception 

 of those species which did not rightly belong there. Their body is 

 soft, contractile, more or less elongated, beset with tentacula similar 

 to those of the ambulacra of the Echini, and are sometimes arranged 

 as regularly as in the latter. The mouth is situated at the anterior 

 extremity of the body, surrounded by appendices, more or less rami- 

 fied and fringed ; the anus is placed towards the opposite extremity. 

 Notwithstanding the elongated form of these animals, by which they 

 more or less resemble worms, we perceive in the interior and even at 

 the surface the radiated disposition of certain parts of their body, 

 which are arranged in vertical bands, extending from the mouth to 

 the posterior extremity. The numerous species which this division 

 now contains renders it necessary to establish several genera, which 



* Translated from the Annates des Sciences Naturelles for May 1837. 



