292 THE CANADIAN NATURALIST. [Sept. 



not " ovarian orifices." The large anterior aperture would thus 

 be the oro-anal spiracle. Applying this system of terminology 

 to other groups, — the so-called ovarian orifice of the Cystidea, the 

 homologous aperture of Nucleocrinus, Codaster, Granatocrinus 

 and of the J^aleozoic Crinoidea generally (but not of the recent 

 forms), should be styled the oro-anal orifice. 



I think that the side of an Echinoderm in which the mouth is 

 situated should be called " anterior" even although the anus and 

 the mouth be confluent in one orifice. Most star fishes have but 

 one aperture for mouth and vent, and yet it is called the mouth by 

 naturalists generally. Why not call the under-side of a star-fish 

 "the anal or posterior side," and the central aperture the 

 " anus? " 



Dr. B. F. Shumard has shown (Trans. Acad. Nat. Sci. St. 

 Louis, vol. 1, p. 243, pi. 9, fig. 4,) that in perfect specimens of 

 P. conoideus Hall, the six summit apertures are closed by several 

 small plates. In a specimen of the same species sent me by Mr. 

 Lyon, in which those plates are partly preserved, I find that 

 there is a small pore in each of the five angles of the central 

 apertures. The five ambulacral grooves enter the interior through 

 these pores. I have copied his figure, but modified it by adding 

 the pores, fig. 15. He also found that the summit of P. sulcatus 

 Roemer, was covered with an integument of small plates, ar- 

 ranged in the form of a pyramid. From these facts he infers 

 that in all the pentremites the summit apertures will be found in 

 perfect specimens, to be closed in a similar manner. 



Dr. C. A. White, at present State Geologist of Iowa, in a 

 paper on the same subject, (Bost. Jour. N. H., vol. 8, p.p. 481 — 

 488,) describes P. Norwoodii Owen and Shumard and P. stelli- 

 forniis, id., as having a similar structure — but he goes further, — 

 he considers the central orifice " not to be the 7noJith," and I 

 believe that he is the first naturalist who ever published such an 

 opinion. His idea of its function is thus expressed : " It seems 

 more probable that, as the ova were germinated within the body, 

 they found their exit through the central aperture, and were 

 conveved along the small central grooves of the pseudambulacral 

 fields before mentioned, beneath the plated integument, to the 

 bases of the tentacula, where they were developed and discharged, 

 as in the true crinoids." I perfectly agree with Dr. White in 

 this view. The central aperture is not the mouth ; in fact, it is 

 not a natural orifice, but a breach in the summit, caused by the 



