390 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



Family Smittinidac Levinsen, 1909 



This is a large and varied family, but on the whole is fairly distinct. 

 The frontal is an olocyst with few to many areolar pores, or a pleuro- 

 cyst which develops above the olocyst from the margin inward to the 

 center of the front, or a tremocyst with numerous evenly distributed 

 pores. (Additional pores are often present in the pleurocyst, especially 

 near the proximal end, but these seldom approach the region of the 

 aperture and usually leave an imperforate area proximal to it. The 

 nature of the growth of this layer may be observed on young marginal 

 zooecia.) The primary aperture is somewhat semicircular (sometimes 

 nearly round, occasionally a little asymmetrical) and usually there are 

 cardelles and a lyrula. The secondary sinus is often well developed 

 proximally. Oral spines are of common occurrence but may be entirely 

 wanting. The operculum is thin and delicate and there is usually no 

 evidence of a vestibular arch. Multiporous rosette plates are the usual 

 means of communication in the lateral and distal walls, but pore chambers 

 (dietellae) may be present. 



Avicularia are very regularly present, though in individual zooecia 

 they may be wanting, and they are of two categories: (1) median, 

 suboral avicularia in which the avicularian chamber extends across the 

 front to communicate with an areolar pore on each side immediately 

 proximal to the aperture, and (2) frontal avicularia of various forms 

 and sizes. Only the suboral, or only the frontal avicularia may be present, 

 but both kinds are frequently found on the same zooecium. Giant 

 interzooecial avicularia also are occasionally found. 



The ovicells are hyperstomial, usually prominent at first but often 

 becoming deeply embedded in the later stages of calcification. The sur- 

 rounding zooecia often contribute to the formation of the secondary 

 ooecial layer. The ovicell may be imperforate, it may be perforated by 

 numerous small or larger pores, by a few larger pores centrally placed, 

 or in a few species there is a single central pore (occasionally doubled). 



SMITTINA, sens lat. 



The genera Porella Gray and Smittina Norman have been much 

 confused. Formerly nearly all of the species with a median suboral 

 avicularium were allocated to Porella but later many of these were 

 transferred to Smittina, especially those with a well developed lyrula. 

 The lyrula is rather variable, however, and there has seemed to be 

 no sharp line of division on this basis. There are other criteria to be 



