284 Dr. P. H. Carpenter on the 



the ambulacra, present characters of much systematic 

 value"* 



Now in the first place I never said that I consider the 

 hydrospires as very characteristic or of much systematic 

 value ; and secondly, even if I had said so, I do not see how 

 the fact of their being respiratory organs can in any way 

 affect the merits of a classification which is partially based 

 upon their structure and distribution. It is at any rate 

 better than one which depends upon " the number and com- 

 position of pieces forming the exoskeleton " of a Pentremites ; 

 for this number is always the same, as Mr. Hambach admitsf. 

 He appears to ignore the fact that other genera J of Blastoidea 

 have been established besides Pentremites, Cod aster, and 

 Orophocrinus § ; and he entirely forgets that while Mr. 

 Etheridge and myself were writing about the classification of 

 all the Blastoids his remarks are simply entitled " Notes about 

 the Structure and Classification of the Pentremites." But 

 even with this restriction I am at a loss to know how Mr. 

 Hambach can follow his own rule and classify the various 

 types which have been described under the generic name Pen- 

 tremites by the number and composition of the pieces forming 

 their exoskeleton. For lie says || : — " The exoskeleton, i. e. 

 the calcareous parts forming the calyx, as also the relative 

 position of each, is the same in all Pentremites as well as in 

 those recently separated from them (whether they are of a 

 globose, truncate or clavate form, with small or broad ambu- 

 lacral fields), and is certainly of far greater importance than 

 the mere softer interior organs, to which belong the hydro- 

 spiric sac and other vessels. The calcareous portion of the 

 ambulacral field consists only of lancet pieces and poral pieces." 



Thus, then, every so-called Pentremites has the same number 

 of basals, radials, deltoids, and lancet pieces ; and as Mr. 

 Hambach does not believe in the existence either of the 

 summit-plates or of the covering-plates to the ambulacra, I 



* R. Etheridge, Jun., and P. H. Carpenter, " On certain Points in the 

 Morphology of the Blastoidea, with Descriptions of some new Genera 

 and Species," Ann. Sc Mag. Nat. Hist. ser. 5, vol. ix. 1882, p. 214. 



+ Trans. St. Louis Acad. vol. iv. p. 547. 



\ These are Ekcacrinus, Eleutherocrinus, Astrocrinus, and Stephano- 

 crinus, besides those proposed hy Mr. If. Etheridge, Jun., and myself, to 

 some of which Mr. Hambach takes exception. 



§ Mr. Hambach still persists in calling this type Codonites, u contrary 

 to " the recognized rules of priority in zoological nomenclature. In this 

 respect he has much to learn from his countrymen Messrs. Wachsmuth 

 and Springer. 



|| Trans. St. Louis Acad. vol. iv. p. 547. 



