Prof. Agassiz on the Echinodermafa. 195 



lus and an Echiurus. Lastly, in the order of Echinida he 

 establishes the following genera: — Stronrjylocentrotvs for some 

 new species, Heterocentrotus for the species of which I have 

 formed the genus Acrocladia, Colobrocentrotus for those which 

 I place in my genus Podophora, and PhyUacanthus for the 

 Ciderites with large cylindrical and tuberculated spines. 



M. De Blainville, in the ' Dictionary of Natural Sciences ' 

 (vol. Ix.), only admits in the family Hohthurice the five fol- 

 lowing genera: — Cuvieria, Holothuria, Thyone, Fistidaria and 

 Cuciimaria ; but in the Supplement to his ^ Manuel d'Actino- 

 logie' he divides it into six groups, in which he adopts in part 

 the genera proposed by his predecessors. His articles upon 

 the Echinodermata in the ' Dictionary of Natural Sciences,' 

 and in his ' Manuel d'Actinologie,' which is a systematic col- 

 lection, contain much valuable information upon the entire 

 class. Lastly, the numerous notes appended by M. Desjardin 

 to the third volume of the second edition of Lamarck's ' Ani- 

 maux sans Vertebres,' have in this work brought up the history 

 of the Echinodermata to the actual state of the science. 



At my sohcitation Professor Valentin has undertaken for 

 the present publication, a general revision of the anatomy of 

 the Echinodermata ; his first monograph, embracing the ana- 

 tomy of the genus Echinus, is already completed. Eight folio 

 plates, drawn under the superintendence of M. Valentin by 

 M. Dickmann, a very skilliil draughtsman, are also litho- 

 graphed, and the accompanying text is going through the 

 press at this moment. The scientific world knows what it 

 may look for from the dissecting-knife and the pen of M. Va- 

 lentin ; I shall only remark here, in justice to his disinterest- 

 edness, that M. A'^alentin, at his own expense, has made a voy- 

 age along the coasts of the Mediterranean for the special pur- 

 pose of devoting himself to the necessary researches for com- 

 pleting this undertaking. i^Ionographs upon the organization 

 of these animals are at the present time so much the more 

 necessary, as since the labours of Tiedemann and Delle 

 Chiage, the greater part of the investigations made in this 

 department of science relate to points of detail. The article 

 ^Echinodermata^ by Sharpey, in Todd's ^ Encyclopredia of 

 Anatomy and Physiology,' contains a summary of all that is 

 knoAvn of the organization of this class of animals. 



Some monographs of very recent date have helped to ex- 

 tend this branch of scientific research. M. Grube has pub- 

 lished a very complete anatomical description of the Sipun- 

 culus nudus, accompanied with well-executed illustrations 

 (Mailer's Archiv, 1837, P- 237). M. Krohn (ibid, 1839, p.348) 



