276 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



Family Hippothoidae Levinsen, 1909 



"The zooecia become calcified from behind in successive zones for- 

 ward, leaving at the surface more or less salient lines of growth, and are 

 furnished with a variable number of dietellae." (Canu and Bassler, 

 1920:325). In Hippothoa, Chorizopora and Hincksipora the frontal is 

 imperforate; the first two of these and Trypostega have hyperstomial 

 ovicells, they are endozooecial in Hincksipora, and none have been found 

 in Harmeria; in Hippothoa, Chorizopora and Trypostega there is a 

 distinctly sinuate aperture but there is no indication of a sinus in the 

 others ; in Trypostega and Chorizopora there are interzooecial avicularia 

 in line with the zooecial axis, but none at all in the other genera. As 

 pointed out by Canu and Bassler, the family is not a natural one and 

 appears to be a group of primitive Ascophora associated by their simplicity 

 rather than by more positive factors. 



Key TO Genera of Hippothoidae 



1. Zooecial front imperforate (except areolar pores) 2 



Frontal more or less perforated 4 



2. Avicularia distal to and in line with the zooecia . . Chorizopora 

 Avicularia wanting 3 



3. Ovicell hyperstomial, porous; frontal thin .... Hippothoa 

 Ovicell endozooecial, frontal excessively thick . . . Hincksipora 



4. The whole frontal finely perforated ; small avicularia on zooeciules 



in line with the zooecia Trypostega 



Pores limited to a definite disto-central area, avicularia and ovicells 

 wanting Harmeria 



Genus HIPPOTHOA Lamouroux, 1821 



The zooecia are usually uniserial, but may be multiserial and loosely 

 attached to each other with small fenestrae between. There are no frontal 

 pores but the ovicells are porous. The fertile zooecia (gonoecia) are 

 usually different in size from the infertile ones and may be different in 

 form. The aperture has a shallow sinus. The growth ridges on the front 

 are transverse and usually very conspicuous. No spines, no avicularia. 

 Genotype, //. divaricata Lamouroux, 1821. 



