On the Production of Mollusks in Holothurise. 103 



Affinities and differences. — In its general outline H. gibberulus 

 resembles the young of H. agariciformis, but its anterior gibbous 

 crest distinguishes it at a glance from that species, and I know 

 of no other form for which it could be mistaken. 



Locality and stratigraphical range. — This is a rare Urchin : I 

 know only four British specimens, the best of which, from the 

 cabinet of W. Walton, Esq., of Bath, has served for the foregoing 

 description, and to whom I beg to record my thanks for his 

 courtesy in forwarding it. This Urchin was collected by that 

 gentleman from the Inferior Oolite in the parish of Charlcomb 

 near Bath, from whence three of the four specimens were ob- 

 tained ; the fourth was found in the Inferior Oolite of Dorset- 

 shire, and is in the Museum of Practical Geology. 



History. — First figured and described by M. Agassiz, who 

 only knew of two specimens from the Inferior Oolite of Switzer- 

 land ; afterwards by M. Desor in his valuable monograph on the 

 Galerites, and now described as a British fossil for the first time. 



[To be continued.] 



VIII. — Upon the Production of Mollusks in Holothuriae. 

 By Prof. Muller*. 



In our last Number we gave a translation of a very remarkable 

 paper bearing the above title, which had been read by Prof. "Mul- 

 ler before the Academy of Sciences in Berlin on the 23rd of Oc- 

 tober 1851. Considering the length of this communication, the 

 elaborate manner in which it entered into details, the importance 

 and very startling nature of the presumed discovery, the dignity 

 of the scientific body to which it was addressed, and the high 

 reputation of its author, we did not doubt that the statement as 

 to facts was complete, and that the reasonings thereupon were 

 mature and well-weighed. Although therefore we could not 

 help pointing out the most obvious weak points of the argument, 

 respect for what seemed the fixed conviction of a very eminent 

 man, prevented more than a feeble protest. 



The new essay, whose title stands at the head of the present 

 article, bears date December 1851, five or six weeks therefore 

 later than the previous one, and this five or six weeks has been 

 sufficient to effect a very considerable change in the whole aspect 

 of the matter ; the alteration being such, we are happy to say, as 

 more than justifies the criticisms upon which we ventured. 



Let it not be imagined that the differences are such as would 



* Ueber die Erzeugung von 

 M'vlkr's Archiv, 1852, No. 1. 



Schnecken in Holotburien. Von Joh. Muller. 



