THE CYSTIDEA 



49 



well be distinguished from Eocystites (?) longidactylus, Walcott (1886), that 

 species must be taken as the example of the family (Fig. X.). Thecal 

 plates numerous, irregular, " varying in form, size, and surface characters 

 on the same body." The two important points are : the varying develop- 

 ment of radiating stereom-folds on some of the plates ; the presence around 

 the mouth of not less than ten biserial brachioles, with long covering- 

 plates (" short pinnulae," Walcott). This type, therefore, is intermediate 

 between Amphoridea and Rhombifera, and its occurrence at so low a 

 horizon is fortunate for the phylogenist. This family Eocystidae in no 

 way corresponds to Haeckel's Eocystida, which, like his Eocystis> is a 

 purely imaginary creation of no systematic validity. 



FAMILY 4. ANOMALOCYSTIDAE. Theca compressed in the plane of the 



FIG. X. 



Eocystis longulactitlus. 1, portion of test much enlarged, showing variation in size, outline, 

 and markings of plates, some of which have apparent pores at their edges ; 2, upper part of 

 a specimen without test, showing portions of brachioles and impressions of covering-plates. 

 With kind permission of Dr. C. D. Walcott. 



thecal apertures, one side tending to be convex, the. other concave. 

 Plates of the two sides enclosed by a common frame of marginals. Plates 

 of concave side tend to be fewer and more regular than those of convex, 

 but never achieve bilateral symmetry as do the latter. Tapering stem of 

 polymeric columnals at one end of theca ; at the opposite end are the 

 apertures, with function still uncertain. In some genera, spines ("arms" 

 of most writers) are known, one at each upper angle of the theca. Orna- 

 ment of granules, which on the theca tend to run in transverse, wavy, 

 sub-parallel lines, simulating the scale-markings of some Crustacea. No 

 pores. J. Walther (1886) and Haeckel (1 896) have considered the bilateral 

 symmetry primitive, and homologous with that of the Dipleurula ; 

 but M. Neumayr (1889) maintained that the symmetry of the two was 

 different. The evidence suggests that the evolution was towards greater 



