44 REVIEWS CANADIAN ORGANIC REMAINS. 



Cystidese, by Mr. Billings. To this paper we invite more especially 

 the attention of our readers, as it contains a preliminary dissertation, 

 with many illustrative wood-cuts, in addition to the lithographed 

 plates, on the general history and organization characters of this 

 extinct and interesting type of ancient life. Mr, Billings has thus 

 kept in view the wants of the general student, whilst affording infor- 

 mation of a new and purely original character to those already familiar 

 with these details. It would scarcely be fair to our author to quote 

 from this introductory portion of his work, as the necessarily restricted 

 length of our quotations, combined with the absence of explanatory 

 wood-cuts, would fail to convey a just idea of the perspicuous and 

 comprehensive manner in which the various details of the subject are 

 classified and set before the reader. This, however, we regret the less, 

 since, in accordance with the suggestion of Sir William Logan, whilst 

 a certain number of copies of these decades is to be reserved for 

 members of the Legislature, the remaining copies of the issue are to 

 be offered to the general public at a merely nominal cost. By this 

 wise innovation, which we trust to see carried out with regard to the 

 other publications of the Survey, the work will be accessible to all 

 who may desire to possess it ; in place of being distributed, as in the 

 case of the Reports already published, amongst a few persons only, 

 and of whom the majority, perhaps, would take but little interest in it. 

 One of the more interesting points discussed by Mr. Billings in his 

 general review of the structural characters of the lower echinodermata, 

 relates to the so-called ambulacral system in the extinct crinoids. As 

 in these ancient forms, the ambulacral grooves occur only in the arms 

 (apart from the pseudambulacra of the Pentremites and other Blas- 

 toidea), the aquiferous and other vessels of the ambulacral system — 

 which in the star-fishes and recent crinoids, issue from the mouth and 

 pass outwards along the grooves — must, in the opinion of Mr. 

 Billings, have entered the body through special pores situated at the 

 respective bases of the arms. The truth of this happy suggestion — 

 difficult of general proof, from the imperfection of specimens — has 

 been established by Mr. Billings, and also independently by Professor 

 Huxley, in several species of crinoids belonging to different genera. 

 With regard to the much-disputed position of the oral aperture in the 

 true cystideans, Mr. Billings agrees with De Koninck and others — in 

 opposition to the older view of Von Buch, and to the, perhaps, still 

 general opinion (see Pictet, McCoy, &c.), based on certain analogical 



