in Melicertitidte and other Fossil Bryozoa. 49 



differs somewhat from any with which I am acquainted, but 

 nevertheless reminds us of avicularia and not at all of ovi- 

 cells. 



In M. cenomana, d'Orb., there are some large broken-down 

 cells which I should be inclined to consider avicularian ; but 

 as the preservation of the specimen is unsatisfactory, this 

 must remain uncertain. There is in another part an inflation 

 round which the zooecia are irregularly grouped ; above the 

 lower central zooecium there is a semicircular depression with 

 a few perforations, giving it the appearance of an " area " 

 like those found in the ovicells of so many CelleporcB &c. I 

 hope that this may receive further investigation from some 

 one possessing better specimens. 



Finding a character so distinctly Chilostomatous as avicu- 

 laria, it is necessary to examine more carefully the others ; 

 and first, as to those on the surface, the front is punctate, 

 with larger pores than those of the Cyclostomata. These 

 have been overlooked, as the fossilization of Cretaceous forms 

 makes it often impossible and usually very difficult to distin- 

 guish such surface-markings ; but in sections they are 

 readily seen. In figure 2 they are shown all over the surface, 

 though, as a matter of fact, they can only be distinguished 

 in a few zooecia. 



Over the aperture of some zooecia there is a thin calcareous 

 plate, but in others there is at a lower level a very peculiar 

 partial closure, formed by three, or sometimes four, calcareous 

 growths, starting from the side and uniting in the centre. 



We thus find externally points which indicate that we are 

 not dealing with a simple Cyclostomata, and examination of 

 the interior structure is quite as convincing on this point. In 

 transverse sections (figs. 5 and 11) a contraction formed by a 

 curved plate is seen on each side just below the opening. 

 Possibly an operculum has an attachment here, but of this I 

 have not been able to satisfy myself. In longitudinal sections 

 (fig. 4) there is also a projecting plate just behind the front 

 wall ; and although I am not acquainted with exactly similar 

 contractions in any Chilostomata, they seem to indicate Chilo- 

 stomatous afiinities, and nothing of the kind is known in the 

 simple tubular Cyclostomata. The central portion of the 

 zoarium, however, consists of parallel plain tubes, and cer- 

 tainly tins portion resembles the structure of many Cyclo- 

 stomata. The lateral walls of the zooecia in the wider part 

 and also at the commencement of the tubular portion show 

 the beaded structure * which I have described in Heteropora 



* " On the Occurrence of Recent Heteropora,''^ Journ. Roy. Micr. Soc. 

 vol. ii. p. 3n0. 



Ann. & Mag. N. llist. Ser. G. Vol. viii. 4 



