NATURAL SCIENCES OF PHILADELPHIA. 115 



In the first two species the opercula are slightly convex, in the latter, con- 

 cave, and with an excentric opening. 



Several species are decorated with spinules, rising from the margins of the 

 tube orifices, and from the interstitial spaces. One of these, which attracted 

 the attention of Milne Edwards, induced him to create for it the genus De- 

 kayia. This spinulosity is not a confluent character, and has, in my estima- 

 tion, no more importance than the hairs of a plant have, in regard to its gene- 

 ric position. 



The so called Dekayia aspera occurs in the blue limestone of Ohio and 

 Indiana, in which several other spinulose forms are found. One of them 

 grows in small ramulets, with somewhat oblique, very minute orifices ; some 

 of its specimens are entirely smooth, without showing any signs of detrition ; 

 in others the surface is raised in scarcely perceptible, obtuse nodules ; and 

 finally, some are found with a perfectly hirsute surface. Also some speci- 

 mens corresponding with McCoys Nebulipora lens, are decorated with quite 

 prominent spinules ; likewise some larger hemispherical masses, considered to 

 be Ch. petropolilanus, and a species similar to Chaetetes frondosus. 



From the shales of the Hamilton group of New York and Michigan, I know 

 also several species of spinulose Chaetetes forms. 



The stellate form of orifices, which is least expected to be seen in Chaetetes 

 or in a Bryozoon, nevertheless is represented in some species of the Chaete- 

 tes family. 



A few specimens found at Cincinnati, which in all particulars agree with 

 Chaetetes frondosus have from three to five longitudinal ridges projecting into 

 their tube cavities, by which the orifices acquire a florifortn shape. In other 

 specimens of the same species the orifices are round, without any traces of 

 stellate character; even in the mentioned specimens, not all orifices are stel- 

 late. The stellate orifices of Callopora Jlorida are made known by Hall ; sev- 

 eral other species of it are of the same character, and also in the genus Fis- 

 tulipora we will meet with floriform orifices. 



The question now is, have we to consider this stellate character as a seri- 

 ous objection to the bryozoic nature of Chaetetes and the allied genera ? 



I think not, for two reasons : 1. This radiate structure cannot be the ex- 

 ponent of a character which is essential to these organic beings, or it would 

 be invariably developed. 2. These projecting lamellae are not the equivalent 

 of the radial organs in corals. Their number is not constant enough for that, 

 and their distribution indicates frequently an unsymmetric bilateral, and not 

 a radial plan. In some species there are only two such projections on one 

 side of the tubes, while the other side is smooth ; in others, with a larger 

 number of lamellar projections, they generally form two opposite groups, 

 and are rarely found disposed at equal distances around the circumference. 



The relations between Chaetetes and some acknowledged bryozoic forms of 

 the paleozoic era are so great, that if radial structure should be considered 

 incompatible with the polyparium of a Bryozoon, I would rather remove 

 the whole assemblage from the bryozoa, than to separate Chaetetes and some 

 others from them. 



In the blue limestone of Madison and Richmond, Ind., a well marked form 

 of Chaetetes is found in abundance, which I do not see described. I propose 

 for it the name Chaetetes quadratics. 



It grows in coarse ramifications, with an even or slightly monticulose sur- 

 face. Tube orifices vary in size in different specimens from one-fourth to 

 one-third of a millimeter ; those on the maculae are somewhat larger ; they 

 are contiguous, polygonal or quadrate, separated by thin walls. Intertubular 

 cells entirely wanting. 



The quadrate tube form is particularly obvious on the terminal surface of 

 branches, or on transverse sections. On the sides of the branches the quad- 

 rate tube form gives the surface a fanciful appearance, which I cannot bet- 



1866.] 



