94 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 16 



Paracyathus tiburonensis Durham (?) 

 Plate 13, fig. 56 



Paracyathus tiburonensis Durham (1947), Geol. Soc. Am., Mem. 20, 

 pp. 35-36, pi. 3, figs. 5, 6. 



The costae of P. tiburonensis are usually wider and more rounded 

 than the comparative ones on P. stearnsii Verrill; the usual costae of 

 P. stearnsii are quite V-shaped, with fewer and heavier granules on top 

 of the ridge, while in P. tiburonensis the granules are more abundant, 

 smaller, and uniform in size and distribution. On the occasional costae of 

 P. stearnsii which are comparable to those of P. tiburonensis, an inter- 

 mixture of numerous small granules and groups of granules fused into 

 larger grains is present. The granules on P. humilis Verrill are like those 

 of P. stearnsii, an intermingling of large and small grains. 



The septa of the types of this species are more delicate than in the 

 material at hand. 



This species is recorded from southwest of Tiburon Island, depth, 

 73 m. 



Hypotype: Cat. no. 56.1 (Sta. 1046-40), a group of individuals. 



Material examined: The hypotype. 



Distribution : Angel de la Guardia Island, shore. 



Genus SPHENOTROGHUS Milne Edwards and Haime 



Sphenotrochus Milne Edwards and Haime (1848), Ann. Sci. Nat., ser. 

 3, vol. 9, pp. 240-241. 

 Genotype: Turbinolia crispa Lamarck. 



Sphenotrochus hancocki Durham and Barnard, new species 



Plate 13, figs. 57a, b 



Corallum of small size, height up to 5 mm, slender, tapering slowly 

 to base, young specimens attached, adults free, with attachment scars at 

 base; calice variable, oval to compressed oval in cross-section, up to 2.5 

 mm in length and 1.5 mm in width; septa 24 in number, septal inter- 

 spaces a little wider than thickness of primary septa, bottoms of inter- 

 spaces flat; major septa may be divided into 4 triads, the terminal triads 

 being composed of one primary and 2 proximal secondary septa, the 

 secondary septa attached to the columella at depth, lateral triads com- 

 posed of 2 primary cycle septa and one second cycle septum attached 

 high up on the columella ; the 2 terminal primary septa are slightly less 

 developed than the remaining primaries and secondaries and do not 



