49 



Melicerititcs durobrivensis, var. parviarmata Greg. 



Meliceritites parviarmata Gregory, Cretac. Hryoz. p. 340, pi. XV, fig. 1. 

 (PI. IV, figs. 7, 19—21.) 



The Zooecia, which are divided by strongly developed marginal ridges are of 

 rather different form and length, but in most cases they are twice as long as broad 

 or even longer. No distinct tubercles. The aperture, the form of which is some- 

 what variable, may sometimes be almost half as long as broad, and the two lateral 

 margins are in most cases more or less distinctly parallel. There is found a strongly 

 developed peristomial thickening, and a very convex operculum with flabelliform 

 striation. No distinct oral ledge. 



The Heierozooecia which are present in large numbers are of very different 

 form and size, the length of the smallest being contained 6 — 7 times in the length 

 of the zooecia, while the larger of them may sometimes attain the length of the 

 latter. Their distal end which is more or less projecting and sometimes forms 

 allmost a right angle with the suboral area contains an aperture of the same form 

 as that of the zooecium, but the larger part of it is closed by a concave lamina 

 which is provided with an opening in the shape of an inverted T. Their distri- 

 bution is very different as they are sometimes placed between the apertures of a 

 number of adjacent zooecia, while in other cases they are irregularly heaped to- 

 gether, partly around the distal end of a zooecium (lig. 7), partly between a num- 

 ber of zooecia, and in some fragments of colonies which have been growing on 

 shells and which are provided with an incrusting base the larger part of the latter 

 is formed by heterozooecia. While that portion of this incrusting layer which 

 immediately surrounds the proximal part of the free stem is composed chiefly of 

 zooecia its peripherica! part almost entirely consists of heierozooecia which there- 

 fore here seem to play a similar role as the kenozooecia forming the incrusting 

 base of a Retepora-co\ony . One of the incrusting bases examined not only covers 

 the one surface of a small fragment of a shell, but also a large part of the oppo- 

 site surface, and here forms an extension 10""" long and 6"^"^ broad, in which 

 there is only found 3 zooecia. 



An Ooechim has been found in one of the incrusting bases. 



No Kenozooecia. 



A Closure of the zooecia by means of a concave lamina has only been found 

 in a few cases (fig. 7). 



The Regeneration. There is found a regeneration both of new zooecia in old 

 ones and of heterozooecia in zooecia (fig. 7). 



I have examined a few fragments from Chatham, Luton, Gillingham (middle 

 chalk) and Evreux (middle Senonian). 



1). K. D. Viriensk. Selsk. Skr.. 7. Række, niiturviilcnsk. nu nialhem. Afd. X. 1. 



