BEITISH PALAEOGENE BBZQZOA. 257 



Distribution. London Clay, Haverstock TiXW.— Foreign. Oligocene : Latdorf, Magde 

 burg, &c., Germany. Palaeogene : New Zealand. 



Type. Brit. Mus. No. 49656. 



Figures. PI. XXXII. fig. 3 a. Part of zoarium, including an ooecium. Fig. 3 b. 

 Transverse section. 



Affinities. Busk has divided the genus Idmonea into two groups : in one the 

 zooecia all open in two lateral groups and the two innermost ones are the longest ; in 

 the second, corresponding to the genus Tervia of JuUien, the outermost are the longest 

 and between the lateral series there are some zooecia irregularly scattered. A third 

 group may, however, be added, including species, such as the present, in which the 

 outermost zooecia are the longest, but in which there is only a single median row of 

 zooecia, and the lateral series are opposite. 



I am aware of the existence of only six specimens of Idmonea from the London Clay ; 

 two of these are quite unrecognizable internal pyritous casts, one of which is identified 

 by Mr. Vine as Idmonea coronopus, Defr., and the other as /. gracillima. A specimen 

 which Mr. Vine tells me is that figured by him as the former is now in the British 

 Museum Collection, but it is labelled, and correctly so, from the London Clay of 

 Sheppey. Mr. Vine [b, p. 165, pi. v. fig. 12] has figured a third specimen also as 

 Idmonea gracillima, Reuss, but it is an Enfalophora. The remaining three small 

 specimens belong one to each of these three groups of Idmonea. This helps one to 

 realize that the British Eocene Bryozoan fauna was a singularly diversified one. 



Lonsdale [No. 2, pi. ix. fig. 24] has also figured a specimen as Idmonea coronopus, 

 but the figure is unrecognizable and I have not been able to find the specimen. 



The only noticeable difierence between the London Clay specimen and the type 

 figure is in the greater length of the zooecia in the former ; but that may be only due 

 to the fragments having come from a difi"erent position in the zoaria. The New 

 Zealand specimen is more doubtful ; Hutton quotes it, but Waters, in his paper on the 

 New Zealand Cyclostomata [No. 8, pp. 387-350, pi. xviii.], does not refer to it. 

 Miss Jelly [No. i, pp. 118, 119] makes it a synonym of /. milneana, D'Orb., but I fail 

 to see why it should be included with this rather than any other species of the genus. 



Species 2. Idmonea bialternata, n. sp. 



Diagnosis. Zoarium sinuous, in thin elongated branches, evenly rounded in front, 

 with a flattish curve at the back. 



Zooecia of medium length, thick, with large apertures ; walls granular. They are 

 arranged in two pairs ; each pair open close together ; the two pairs are placed alter- 

 nately. Peristome thick, plain. 



Ooecia : % a small dilatation at base of the inner zooecia. 



Distribution. London Clay, Islington. 



Type. Brit. Mus. No. 49662. 



