628 



WM. H. EASTON 



Next (fig. Id) each cardinal quadrant con- 

 tains one metaseptum and each counter 

 quadrant contains two metasepta. It will be 

 noticed that the metasepta of the left 

 counter quadrant are aberrant in that they 

 lean toward the alar septum and that some 

 of them may not reach the axis (figs, lc— If). 

 Traces of tabulae can be observed in the 

 last mentioned stage (fig. If), and the alar 

 pseudofossula is developed only on the right 

 side of the coral. The right alar pseudo- 

 fossula still persists when 14 major septa are 

 present (fig. 2), and each cardinal quadrant 

 has one well developed metaseptum at- 

 tached to the cardinal septum. The cardinal 

 fossula soon becomes apparent but the alar 

 pseudofossulae are represented only by 

 slightly wider loculi than occur elsewhere; 

 the cardinal quadrants each contain two 

 metasepta and the counter quadrants three 

 or four (fig. 3). When 16 major septa have 

 been inserted (fig. 4), there are three meta- 

 septa in each cardinal quadrant and three 

 or four septa in each counter quadrant, 

 but several septa have retreated a short 

 distance from the axis. At full maturity 

 (fig. 5) there are 22 major septa, of which 

 three are in each cardinal quadrant and six 

 in each counter quadrant, thus, the counter 

 quadrants are accelerated by the time ma- 

 turity is reached. Amplexoid retreat is very 

 poorly shown, inasmuch as those septa 

 which do not reach the axis are either fused 

 near their axial edges, or else lean against a 

 neighboring metaseptum. The amplexoid 

 condition is developed by middle maturity, 

 nevertheless, as shown by a section just 

 below a tabula (fig. 7). 



Comparison. — This species can be distin- 

 guished externally from the other species of 

 Amplexus by the small size of the corallites, 

 their contorted shape, nearly cylindrical 

 mature portions, calical method of increase, 

 occasional development of spines on one 

 side, about twice as many septal grooves as 

 septa, and by the insertion of two adjacent 

 septa as a pair. 



Remarks. — Septal notation was verified 

 through study of the septal grooves wherever 

 possible. In this regard, it was observed that 

 although minor septa are nowhere de- 

 veloped, a septal groove usually occurs be- 

 tween major septa, hence there are usually 

 about twice as many septal, grooves as septa. 



Ontogenetically, this species is charac- 

 terized by the slow rate of insertion of major 

 septa, by marked acceleration of the counter 

 quadrants in mature stages, and by very 

 poorly developed amplexoid retreat. 



Phylogenetic relationships are with the 

 so-called "zaphrentid" types, except that 

 the fossulae are poorly developed and pri- 

 mary septa tend to remain fused axially. 

 A. adnatus appears to be closely related to 

 A . geniculatus. 



Apical portions of most corallites are so 

 contorted and spinose that study of epithecal 

 ornament is unsatisfactory, however, it was 

 noted in some specimens that the cardinal 

 position is on the convex side of the corallite. 

 It is not known how general this may be, for 

 the cardinal position was also observed to 

 be on some other side in a few specimens. 



Wherever observed, the corals were at- 

 tached by spines to a fragment of a fenestel- 

 lid bryozoan. One coral has two distinct and 

 separate patches of spines and is geniculate 

 in such a manner as to suggested that the 

 animal originally was recumbent along a 

 bryozoan frond and then altered its direc- 

 tion of growth in order to make the corallite 

 vertical, but the bryozoan frond either broke 

 or its position was changed so that the coral 

 was again recumbent and sent out spines. 



Amplexus dilatatus Easton, n. sp. 

 Plate 85, figure 10; plate 86, figures 4, 5 

 Caninia n. sp. Weller, 1920, Illinois Geol. Survey, 

 Bull. 41, pp. 170, 173. 



Externals. — Curved ceratoid corals; epi- 

 theca nearly smooth with encircling wrinkles, 

 relatively faint septal grooves and inter- 

 septal ridges, occasionally with sparse 

 spines; calyx rather deep, vertically walled; 

 calical increase observed, with epitheca 

 grown over old calyx. Mature specimens 

 about 3 cm. long; diameter of calyx about 

 10 mm. 



Transverse sections. — 'Mature section of 

 holotype (pi. 86, fig. 4b) has 27 major 

 septa extending about half the radius, of 

 about equal strength but cardinal and coun- 

 ter septa are slightly longer than other major 

 septa; minor septa short or rudimentary. 



In early maturity (fig. 4a) holotype has 

 19 major septa; cardinal septum short; 

 metasepta of cardinal quadrants pinnately 

 arranged ; alar septa almost reach axis; septa 



