1870.] Geology and Paleontology. 541 



dual species may have been gradually very much modified in time, 

 so as to suit the conditions under which it had to exist ; but at the 

 same time everyone who has studied with any degree of care any 

 class composing the animal kingdom, must frankly admit that there 

 are so many inexplicable sudden appearances of entirely distinct 

 forms, with no apparent links connecting them with those that 

 were antecedent or even contemporaneous, that it is impossible to 

 arrive at any definite conclusions as to what extent species are de- 

 rived from their predecessors." 



New British Brachiopod. — Mr. E. Kay Lankester describes a 

 new species of Terebratula from the (Portlandian ?) " Drift " of East 

 Anglia, which he has named T. rex ; it is a remarkably large form. 



Cephalaspis Dawsoni, sp. nov. — The same gentleman describes 

 a nearly perfect Cephalaspidean Fish from the Silurio-Devonian 

 beds on the north side of (xaspe Bay, Canada, associated with 

 plant-remains. It is named after Principal Dawson, of Montreal. 



The Structure of the Crinoidea, Cystidea, and Blastoidea. — 

 We have lately received considerable additional information upon 

 this subject from the pen of Mr. E. Billings, the able Palaeontolo- 

 gist to the Geological Survey of Canada.* In the first part of his 

 paper Mr. Billings considers the position of the mouth in relation 

 to the ambulacral system. 



Earlier palaeontologists described the large lateral aj)erture in 

 the Cystidea as the mouth. Yon Buch, Forbes, Hall, and Billings 

 himself, in his first paper, adopted the view that this was not the 

 mouth, but an ovarian aperture, and that the smaller orifice, usually 

 situated in the apex, from which the ambulacral grooves radiate, 

 was the true oral orifice. Subsequently (in 1858) Mr. Billings 

 re-investigated the subject, and came to the conclusion that the 

 lateral aperture was really the mouth, or serving as both oral and 

 anal aperture in those species not possessing distinct orifices. The 

 small apical orifice was determined to be an ambulacral aperture. 



To this view Prof. Wyville Thomson demurs, on the ground 

 of the want of analogy in the rest of the class. Mr. Billings re- 

 plies that in this class the position of the various organs in relation 

 to each other, and also to the general mass of the body, is subject 

 to very great fluctuations. Thus the mouth and vent are separated 

 in some of the groups, but united in others ; while either or both 

 may open out to the surface directly upward or downward, or at 

 any lateral point. The ovaries may be either dorsal or ventral, 

 internal or external, and associated with either the mouth or the 

 anus, or with neither. The ambulacral skeleton may be imbedded 

 in and form a portion of the general covering of the body, or lie 

 upon the surface, or be borne upon free-moving arms. Although 

 these characters are constant, or nearly so, in the same family, in 

 * See Silliman's ' American Journal of Science.' 



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