530 PROCEEDINGS OF THE NATIONAL MUSEUM vol.84 



tionally in less vigorous colonies cyclosystems with only one gastro- 

 zooid (and hence one gastrostyle) are found. Whether this condition 

 is of generic or even subgeneric value only more knowledge of the 

 Stylasterina will determine. 



The number of tentacles of the gastrozooid varies from 5 to 8 and 

 is commonly 6. Aloseley (1879, p. 471, pis. 39, 40)^ suggests that 

 the presence of 12 tentacles on the gastrozooid may characterize 

 Allopora and 8 Stylaster. But it has been shown (Hickson and 

 England, 1905, p. 7) that the number of tentacles in Stylaster is 

 variable, S.Jilogranus ha\'ing 4, 5, 6, or 7. 



This species has been found only at lowest tide on the exposed 

 coast from Monterey Bay to a few miles south of Carmel Baj^ The 

 type colony, along with several others, hves in a small grottohke 

 cavity, through which there is free circulation of water. Here they 

 form lichenhke splashes of ruddy purple in contrast to white, scarlet, 

 and yellow sponges, orange and bronze hydroids and bryozoans, and 

 brown tunicates. 



In 1919 the type colony alone hved in this grotto. Then it meas- 

 ured about 50 mm in diameter; now it measures 300 by 250 mm. 

 From time to time sponges and tunicates that encroach upon it have 

 been removed. 



The real home of the species is probably in tbe dimly Ugh ted region 

 below lowest tide, as its occurrence in the intertidal zone is rather 

 sporadic. Conditions at the type locahty favor the upward migra- 

 tion of subtidal species. 



ALLOPORA PETROGRAPTA. new species 



Plate 54, Figures 5, 5a; Plate 59, Figure 4 



Diagnosis.— Colony thin, encrusting; differing from A. porphyra 

 in having smaller cyclosystems with normally only one gastrostyle; 

 differing from A. papillosa in having a thicker gastrostyle, the rounded 

 summit of which occupies the greater part of the breadth of gastro- 

 pore when viewed from above; the gastropore less funnel-shaped and 

 more tubular; surface of coenosteum with finer texture than in 

 papillosa. 



Description. — The material consists of five small fragments. Two 

 of these, constitutuig the type, comprise the greater part of one 

 colony (12 mm broad and 10 mm high), which covered a Balanus. 

 An infant colony covers a barnacle only 6 mm broad. Colonies 

 may reach a diameter of a foot or more, as observed by E. F. Ricketts. 



The outline of cyclosystem resembles that of papillosa in its usual 

 lack of symmetry, there being 3 to 8 short, deep dactylotomes with 



» He says 6 tentacles for Stylaster but means 8; so stated on p. 477. 



