246 Notes and Comments. 



organic bodies transparent and translucent ' by the employ- 

 ment of the refraction of light. Dr. S. F. Harmer, F.R.S., 

 declared the process was a remarkable one. It offered 

 peculiar advantages for the study of the internal structure of 

 animals. You could take a rat and prepare it in a certain way, 

 put it in certain solutions specified, and it would become 

 extremely transparent, so that you could see the details of the 

 skeleton through the skin and muscles. He desired to make 

 use of the process at the South Kensington Museum. The 

 general principle of making objects transparent by putting them 

 in liquids of suitable refractory indices they knew about before 

 the patent, and the patentee could not claim any patent rights 

 in general scientific principles. 



ECHINOIDEA HOLECTYPOIDA. 



Mr. H. L. Hawkins has a paper in The Geological Magazine 

 on ' Morphological Studies on the Echinoidea Holectypoida 

 and their Allies.' Dealing with the Type of Pygaster he states : 

 ' For the present purpose it is sufficient to note that there 

 exists such a species as Pygaster semisulcatus, figured by 

 Phillips (Geol. Yorks.) under the name of Clypeus, though not 

 described by him ; and that it was originally found, and may 

 yet be collected, in the Coralline Oolite of Malton. This form 

 must, then, represent the type of Pygaster, the Inferior Oolite 

 species to which the name has been most frequently applied, 

 being here regarded as not even congeneric. Pygaster, with its 

 restored genotype, will include three of the four species 

 described by Agassiz in 1839 — P. patelliformis, P. tenuis, and 

 " P. umbrella " — and so may be taken as expressing most 

 adequately the original meaning of its author. It will absorb 

 the subgenus Megapygus proposed by me in 1912, that name 

 having been given in ignorance of the real meaning of the 

 term " P. semisulcatus ".' He concludes : ' The following list 

 includes all the changes rendered immediately necessary as a 

 result of the previous discussion : — 



Pygaster, Agass., 1836 (incl. Megapygus, Hawkins, 1912). 

 Type, Clypeus semisulcatus, Phill. Corallian (incl. Pygaster 



umbrella, pars, auct.) (non Pygaster semisulcatus, auct.). 

 Plesiechinus, Pomel, 1883 (incl. Pygaster sens, str., Hawkins, 



1912). 

 Type, Pygaster macrostoma, Wright. Bathonian. 

 Generally speaking, Pygaster is a Middle and Upper Oolitic 



group, and Plesiechinus is restricted to the Lias and 



Lower Oolite.' 



: o : 



We have received the Annual Report of the Public Libraries, Art 

 Gallery and Museum Committee of Rochdale, which contains a record of the 

 work done during the year. 



Naturalist* 



