iHvV YORK 

 iiOTANICAL 

 QARObN 



BOSTON 



JOURNAL OF NATURAL HISTORY. 



VOLUME VIL— NO. IV. 



Art. IX. — Observations on the Summit Structure of Pen- 



tremites, the Structure and Arrang-ement of certain Parts 



of Crinoids, and Descriptions of New Species from the 



Carboniferous Rocks at Burlington, Iowa. By Charles 



A. White. 



[Read February 5th, 1862.] 



In the year 1850, Drs. D. D. Owen and B. F. Shumard 

 announced in the Journal of the Academy of Natural 

 Sciences of Philadelphia, (Vol. II. p. 65,) that the mouth 

 and ovarian apertures of Pentremites were, in the perfect 

 state, completely closed by a conical covering of small 

 calcareous plates ; and in Vol. I. No. 2, of the Transac- 

 tions of the Academy of Science of St. Louis, Dr. Shu- 

 mard gives an illustration of the summit of Pentremites 

 conoideus, Hall, showing all the summit apertures to be 

 completely and separately covered in the manner referred 

 to, and makes the following remarks in relation to a speci- 

 men of P. sulcatus, Roemer, which Prof. Swallow discov- 

 ered at Chester, 111. " In this fossil, there rises from the 

 centre of the summit a little pyramid with five salient, 

 and five retreating angles, the salient angles being directly 

 opposite the extremities of the interradial pieces, while 



.JOURNAL B. S. N. H. 61 JANUARY, 186.3. 



