il 



294 University of California Publications in Zoology. [Vol.4 



large, ovate, front wall much elevated in the middle and sloping- 

 down to the lateral margins and toward the base ; wall dense, 

 smooth, areolated round the edge, in yonnger colonies the areolae 

 large with tube-like ridges radiating toward the middle (pi. 20, 

 fig. 53). Orifice circular, with a shallow sinus on the lower mar- 

 gin ; peristome low ; with increase of calcareous deposit, the orifice 

 comes to be sunken deeply. Below the orifice and to one side an 

 avicidarium, av., muMi elevated, forming a mound, av. /»., or 

 rounded prominence which partially hides the orifice ; mandible, 

 man., bent at the tip, narrow, directed outward, or upward ; a 

 short, mucronate process, mu. pro., where the tip of the mandible 

 closes into the beak. In older parts of the colony, zocecia shorter, 

 calcification increased and an avicularium with mandible directed 

 downward in the middle of the front wall. Oaecia smooth, broad- 

 er than high, almost covered by the elevated avicularium on the 

 lower part of the zooecium above. 



The ocecia occur only on the older portions of the colony and 

 each is not only immersed behind the mound of the avicularium 

 above it, but is surrounded by these structures, there being one 

 above the offcium, one below, and one on each side. Avicularia 

 are scattered profusely over the whole surface of old colonies. 



This species described by Hincks from Queen Charlotte Is- 

 lands. Fairly abundant in dredgings from San Pedro to San 

 Diego. 



Myriozoum Douati. 



Myriozoum Donati, 1751. 

 Millepora (part) Pallas, 1766. 

 Myriapora Blainville, 1834. 

 Myriosoum, Busk, 1873-76. 

 Myriozoum, Hincks, 1877. 



Zoarimn incrusting, or erect, branched ; branches cylindrical, 

 obtuse; surface punctured or reticulate. Avicularia when pres- 

 ent, immersed. Orifice with a sinus on the lower margin. 



The three Myriozoa of the Pacific coast assume two hal)its of 

 growth very unlike each other. One species, M. crustaceum, is an 

 incrusting form, never as far as I know, becoming upright. The 

 other two species, M. coarctatum and 31. suhgracile begin as in- 



