THE MOUNT DESERT REGION 319 



frontal membrane of the ' Membraniporidan ' type, which is 

 secondarily covered over more or less completely by a frontal 

 arch resembling in a general way the frontal wall of the 

 Ascophora. In its mode of development, however, it is quite 

 different, as it is formed by the union of a series of flattened 

 marginal spines, leaving pores or lacunae between them. This 

 is shown both by the mode of development and by dissection. 

 In other cases, the most advanced, there is only a small centro- 

 distal area of the front wall that is so formed, and Harmer 

 (1926, pp. 471-472) suggests that the area represents a re- 

 duced frontal shield which is supplanted over most of the 

 frontal surface by the partial development of the gymnocyst, 

 which in the Ascophora comes to cover the entire frontal 

 surface. In other words, in this group we have a series of 

 gradations leading from the Membraniporidan to the Lep- 

 ralian type of organization, or intermediate between the 

 Anasca and Ascophora. 



Apparently one may take his choice of placing them all 

 in the Ascophora, as Marcus has done (1922, p. 427) ; of 

 splitting them between the Anasca and Ascophora, as Canu 

 and Bassler have done (1929, pp. 27-30) ; or to hitch them on 

 to the end of the Anasca, recognizing that they constitute 

 an intermediate group, as Harmer has done (1926, p. 470). 

 Until there is further evidence to show differences in the 

 manner of development of the frontal shield between such 

 forms as Cribrilina and Figularia, the writer is inclined to 

 the use of Harmer 's Division Cribrimorpha. If this group 

 is intermediate between the Anasca and Ascophora, the only 

 solution would be to create another suborder, which in the 

 present state of our knowledge would appear at least unnec- 

 essary. 



Cribrilinidae Hincks, 1880 

 CRiBRmiNA Gray, 1848 

 Cribrilina punctata (Hassall), 1842. PL 8, figs. 5-6. (Os- 

 burn, 1912, p. 232, synonymy and reference.) Frequently 

 taken on stones and shells and along shore, at nine shore sta- 



