Morphology of the Blastoidea. 2!)1 



cles, by the fact that the deltoids are very small, inconspicuous, 

 and always confined to the summit. They are thus invisible, 

 in a side view, while the hydrospires communicate directly 

 with the exterior, as in Codaster } without the intervention of 

 any spiracle openings. The same characters distinguish these 

 two species from Mr. Hambach's first division of Pentremites, 

 in which are included P. Godoni, P. sulcatus, and their 

 allies, with well-defined deltoid plates and distinct spiracular 

 openings. 



What grounds, then, has Mr. Hambach for asserting that 

 these two species " can easily be distributed " in either one 

 or the other of his three divisions of Pentremites? Homer 

 has published a good figure of P. caryophyllatus *, with which 

 Mr. Hambach is probably acquainted ; and Billings remarked 

 upon it, " I do not think that such species can be referred to 

 Pentremites ; and if I had specimens before me instead of 

 figures only, I should most probably institute a new genus for 

 their reception "j\ 



But it is in reference to Pentremites acutas that Mr. Ham- 

 bach's assertion appears most surprising. The two original 

 specimens described by Phillips have been in the British 

 Museum for years. They have not been seen by Mr. Ham- 

 bach, and there is no record of the discovery of any others. 

 On the other hand, he cannot but be aware that Billings's 

 suggestion respecting the generic difference of De Koninck's 

 species from the ordinary Pentremite type has been adopted 

 by Mr. Etheridge and myself \; that we have proposed the 

 name Phwnoschisma for the reception of such species as P. 

 acutus and P. caryophyllatus ; that we gave a diagnosis of 

 the genus and discussed its affinities*; and, lastly, that its 

 validity has been recognized by Wachsmuth §. And yet 

 Mr. Hambach, without having seen a specimen of Pentremites 

 acutus at all, or even an acurate figure of it ||, calmly asserts 

 that it " can easily be distributed " in one of his three divi- 

 sions of the old genus Pentremites I 



It is fortunate for science that this method of classification 



* Op. cit. Taf. iv. fiij. 16 c. 



+ ' Annals,' ser. 4, vol. v. pp. 262, 26:3. 



\ 'Annals,' ser. 5, vol. ix. p. 226. 



§ " On a new Genus and Species of Blastoids, with Observations upon 

 the Structure of the Basal Plates in Codaster and Pentremites, '' Palason- 

 tology of Illinois, vol. vii. 1883, p. 252. 



|| The small figures given by Sowerby and Phillips, even if Mr. Ham- 

 bach has seen them, do not show the most striking characters of this 

 species, and are of no u.-^e whatever for cla^sifieatory purposes. 



