184 ANNALS NEW YORK ACADEMY OF SCIENCES 



Heterophrentis prolifica Bill. 



Billings' emended description, 1874 : 



"Corallum simple, turbinate, curved, expanding to a width of from 18 to 2A 

 lines in a length of from 2 to 4 inches. Surface with a few undulations of 

 growth. Septal striae 8 to 10 near the base and 6 to 8 in the upper part in 

 a width of 3 lines. Septa from about 100 to 120 at the margin (where they 

 are all rounded), most common number from 100 to 110. In general they alter- 

 nate in size at the margin ; the small ones becoming obsolete on approaching 

 the bottom of the calice ; the large ones more elevated and sharp-edged. The 

 septal fossette is large and deep, of a pyriform shape, gradually enlarging 

 from the outer wall inwards for one-third, or a little more of the diameter of 

 the coral, at the bottom of the calice. Its inner extremity is usually broadly 

 rounded or, sometimes, straitish, in the middle. It cuts off the inner edges of 

 from 8 to 12 of the principal septa which may be seen descending into it to 

 various lengths. The surface layer of the bottom of the cup extends the whole 

 width, bending downwards a little near the margin, as in Zaphrentis, and 

 uniting with the inner wall of the cup all around. It thus seems to represent 

 one of the tabulae of a Zaphrentis. The following are the principal variations 

 observed in this part of the fossil. 



"1. Specimens with a perfectly smooth space in the bottom of the cup; no 

 columella. 



"2. A smooth space with a small conical tubercle near the center. 



"3. Smooth with a small ridge, two lines in length and half a line in height 

 and width. 



"4. Smooth with a compressed columella 3 lines in length, 2 lines in height, 

 most elevated next to the fossette, gradually declining in height towards the 

 opposite side. 



"5. Smooth spaces very small, columella a low ridge, with a few tubercles on 

 its crest. 



"6. Columella well developed, but with tubercles on it and around it. 



"7. Septa reaching the columella and more or less corrugated and either with 

 or without a columella. 



"In all cases where the columella is elongated, its length extends in a direc- 

 tion from the fossette to the opposite side. In those which have the septa 

 extending to the centre the columella is often represented by a low rounded 

 elevation." ( 12, 2v''6, 237. ) 



In 1900 George B. Simpson published a preliminary description of new 

 genera of Palaeozoic rugose corals, in which he includes several species 

 formerly referred to Zaphrentis. He erected the genus HapsiphyUum for 

 such zaphrentoid corals, which like Z. calcariformis Hall of the St. Louis 

 beds, the genotype, have a horse-shoe shaped inner wall, formed origi- 

 nally by the bending over and uniting of the ends of the septa. The 

 cardinal septum and fossula lie within the area thus enclosed. Another 

 genus made by him is Triplophyllum vith Zaphrentis terehrata Hall as 



