THE MOUNT DESERT REGION 333 



to the posterior border of the semicircular aperture is a dis- 

 tinguishing character. Pointed avicularia are usually pres- 

 ent at one or both sides of the aperture, pointed forward and 

 outward. 



Smittinidae Levinsen, 1909 

 Smittina Norman, 1903 



Smittina trispinosa (Johnston), 1838, and var. nitida Ver- 

 rill, 1875. PI. 10, fig. 6. (Osburn, 1912, p. 246, (Smiftia) for 

 synonymy and references ; 1912 a, p. 286, for Canadian ref- 

 erences and records; Whiteaves, 1901, p. 106 (Smittia), Cana- 

 dian records.) Rare in dredgings, stations 6, 18, 43, 94, and 

 95, not taken at shore stations. Most of the specimens are 

 of the variety nitida, with oval avicularia, but some of them 

 have the pointed avicularian mandibles of the true trispinosa. 

 It is a cosmopolitan species A\^th many varieties. On the 

 American coast the variety arhorea occurs in Greenland, the 

 variety nitida ranges from Hudson Strait to the Carolina 

 coast, and the variety spathidata from thence southward to 

 Florida, Porto Rico, and Curacao. The typical form occurs 

 from Greenland to at least as far south as Cape Cod. 



The zoarium often forms quite thick encrustations on peb- 

 bles and shells. The zooecia have raised borders, marginal 

 pores, and avicularia of pointed or oval form variously situ- 

 ated. Occasionally a number of avicularia are present, but 

 never, as far as I have observed, in the suboral position so 

 common in other species in the genus. The lyrula or median 

 shelf and the lateral denticles are conspicuous. The ooecium 

 is hemispherical and perforated by a number of pores of 

 irregular size and arrangement. Secondary calcification is 

 often very heavy, frequently obscuring the primary charac- 

 ters, the peristome may be raised, especially on the sides, 

 and umbonate processes may appear suborally and on the 

 top of the ooecium. 



Smittina concinna (Busk), 1852. PL 10, fig. 5. (Osburn, 

 1912, p. 247 (Porella), in part, synonymy and references; 

 Whiteaves, 1901, p. 102 (Porella), Canadian records.) Sta- 



