312 BIOLOGICAL SURVEY OF 



It is a striking- species in our fauna, readily distinguished 

 by the presence of 4 to 6 very stout flattened spines which 

 bend across the membranous area. There is a high degree of 

 secondary calcification and in old colonies the short, broad, 

 and flattened ooecium becomes deeply immersed. 



Tegella unicornis (Fleming), 1828. (Osburn, 1912, p. 230 

 {Memhranipora) ', 1912 a, p. 279 {Memhranipora), Labrador: 

 Whiteaves, 1901, p. 96 {Memhranipora), Gulf of St. Law- 

 rence.) This is an abundant species, occurring almost every- 

 where in the region. It was found at fifteen shore stations 

 and forty dredging stations. It ranges from south of Cape 

 Cod to the Arctic Ocean and from the British Islands to 

 Nova Zembla. 



This is a variable species, differing especially in the size 

 and length of the spines, the form of the zooecia, and the 

 presence and arrangement of avicularia. The full comple- 

 ment of spines is four, the anterior pair being small and 

 often wanting. The other pair, just posterior to the oper- 

 culum, are usually very unequal in size and the longer one 

 may be very prominent. An avicularium is usually present 

 at the base of the zooecium mounted on a raised projection ; 

 when an ovicell is present the avicularum appears as if 

 mounted on its anterior surface and is pointed somewhat 

 forw^ard, but wiien the ovicell is absent the avicularium is 

 reversed in position, the mandible pointing backward. 



Tegella unicornis var. armifera (Ilincks), 1880. PL 6, 

 fig. 7. (Osburn, 1912, p. 229 (under Memhranipora arc- 

 tica) ; Whiteaves, 1901, p. 97 {M. sophiae, var. armifera). 

 Gulf of St. Lawrence.) Occurring with the typical form at 

 various stations, but not nearly so abundant. The variety 

 armifera appears to accompany the typical unicornis through- 

 out most of its range. 



A well-marked variety, which differs in the smaller size of 

 the spines, in the presence of a pair of small avicularia situ- 

 ated at the sides of the operculum anteriorly with the man- 

 dible pointing backw^ard. It is the form which was listed by 

 Packard and Verrill as Memhranipora americana d'Orbigny. 



