BRYOZOA. 491 



radiating depressions occupied by angular sub-spherical or flat- 

 tened vesicles; about two or three times the diameter of the zooecia. 

 The space between the disks is taked up by much larger irregu- 

 lar vesicles, being several times as wide as those at the center 

 of the disks. These may represent ooecia. 



Specimens from different localities vary a great deal in the 

 size of the disks and number of ra^-s. Possibly several species 

 have been thrown together, but without more material than is 

 now before me, it would be unwise to establish more species. 

 In the specimen figured the disks are larger than in any other 

 seen by me. 



Position and locality: Hamilton group, Eighteen Mile Creek, 

 X. Y.; Arkona, Canada; Falls of the Ohio; Thunder Bay, Mich. 

 Probably also at Andalusia, 111. 



CYSTODICTYA Ulrich, 1882. 



(Jour. Cin. Soc. Nat. Hist. Vol. V, p. 152.) 

 (For generic diagnosis see page 385.) 



This is one of the most important of the Palaeozoic genera 

 of Bryozoa, being abundantly represented by both species and 

 individuals, in the upper divisions of the age. No species are as 

 yet known from rocks of earlier date than Devonian, but in 

 the Upper Helderberg and Hamilton deposits the genus makes 

 its advent with a comparative!}' strong representation, no less 

 than twenty species having already been described that are 

 referable to the genus. Of these seventeen have lately been 

 published by Prof. Hall as species of Stictopora. Most of them 

 he illustrates, while the descriptions of the others are sufficiently 

 full to enable me to determine their generic relations. The fol- 

 lowing clearly belong to Cystodictya and not to Stictopora,* 



* I find a foot note on p. 10 of a number of plates and explanations which are pub- 

 lished by Prof Hall in advance of his report as State Geologist for 1886. This note reads 

 as follows: "In relation to the genus Cystodictya, I may remark that every species of 

 Stictopora known to me possesses the characters on which the genus Cystodictya has 

 been founded." In answer to this decretory note, I wish to say, that Prof. Hall has 

 either entirely forgotten that his genus Stictopora was founded upon Lower Silurian 

 species of very different structure from Cystodictya, or he has failed to appreciate the 

 really essential characters of the typical species of his genus. He describes the genus 

 with six species in the PaL of New York, Vol. 1, published in 1847. On page 16 we find 

 Stictopora fpnestrata, page 17 .5'. glomerata, p. 50 5. labyrinthica, p. 51 S. ramosa, p. 74 

 the generic description and S.(?'> acnta, and on the page following S. elegantula. Now 



