NATURAL SCIENCES OF PHILADELPHIA. 31*7 



six of the arms, that seems to agree exactly, in structure, orna- 

 mentation, and form, with the last, excepting that its body is not 

 quite so rounded below; and it has a more robust appearance, in 

 consequence of having the ridges up the radial and secondary 

 radial series (particularly the latter), as well as that up the middle 

 row of the anal plates, rather decidedly stouter and more promi- 

 nent. Its arms are also proportionally stouter, and composed of 

 shorter pieces. 



This may be specificall}^ distinct from the last ; but, with the 

 present means of comparison, I prefer to range it provisionally as 

 a variety of the same, under the name Glyptocrinus Dyeri, var. 

 subglobosus. 



Locality and position. — Same as last. 



MOLLUSCA. 



POLYZOA. 



^ PTILODICTYA (STICTOPORA) SHAFFERI, Meek. 



Polyzoum small and delicate, consisting of slender, compressed 

 divisions, that give off on each side rather closely arranged, regu- 

 larly alternating, lateral branches of the same breadth as the 

 main stems, from which they diverge at an angle of about forty 

 degrees ; lateral branches in the same way giving off on each side 

 very short lobe-like, alternating projections ; lateral margins of 

 all parts very narrow, sharp, and minutely striated longitudinally, 

 in well-preserved specimens ; pores apparently without raised 

 margins, more or less oval longitudinally, alternately disposed in 

 longitudinal and oblique rows, so as to present a quincuncial 

 arrangement; the number of longitudinal rows vaiying from five 

 to about seven in the breadth of a stem or branch ; spaces between 

 the pores, measuring transversely to the stems and their divisions, 

 about equal to the breadth of the pores, but greater, measuring 

 in the direction of the oblique and longitudinal rows; all the in- 

 terspaces ornamented, in perfectly preserved specimens, by very 

 minute, more or less waved or flexuous strife. 



Size of entire polyzoum unknown ; breadth of stems and 

 branches, 0.05 inch ; number of pores in 0.05 inch, measuring in 

 the direction of the oblique rows, about 4 to 6, and, in the same 

 space, measuring longitudinally, from 3 to 4. 

 1872.] 



