90 A. H. MACKAY ON 



B. — Dermal Spicules Present. 



3. — Spongilla lacustris. 



1*745. Spongia lacustris, Liuu. 



1*788. " canalium (?), G-meliu. 



1816. Spongilla ramosa, Lamarck. 



1842. '■ lacustris, .Tolinstou. 



1853. " " Lieberkiihu. 



1863. '■ Dawsoni, Bowerbank. 



1863. " paupercula, 



1866. " lacuslris, 



18*70. " Lieberkhùenii, Noll. 



18*75. " jlexispina, G. M. Dawson. 



18*7*7. " lacustris, Vejdovsky. 



18*7*7. " Jordanensis, 



18*79. " lacustroides, Potts. 



1880. " abortiva, 



1880. " mutica, 



1880. " montana, 



1881. " multiforis, Carter. 



1882. " lacustris, Dybowski. 



1883. Etispongilla lacuslris, Vejdovsky. 

 1883. " Jordanensis, " 



1883. Spongilla lacustris, var. ramosa, Retzer. 



1883. " " " Leiberkueknii, Eetser. 



1884. " Lehighensis, Potts. 

 1884. EvspongiUa lacustris, Wierzejski. 



1884. Spongilla lacustris, var. Americana, Carter. 



1885. " lacustris, var. Daivsoni, MacKay. 



Sponge green, generally branching, texture loose. Skeleton spicules fasciculated, 

 smooth, curved, fusiform, gradually pointed, about 0.011 inch long. Dermal or flesh 

 spicules fusiform acerates, curved, entirely microspined, generally less than one-third the 

 length of the skeleton spicules. Statoblast about 0.02 inch in diameter. Granular crust 

 variable in thickness, sometimes even absent. Foraminal tubule infundibular. Stato- 

 blast spicules nearly the same length as the dermals, generally cylindrical. Curved in 

 various degrees, sparsely and strongly spined, especially tow^ards their ends, where the 

 spines are frequently recurved. The number and position of spicules vary with the 

 thickness of the crust. 



Habitat. — The most common of fresh-vrater sponges. Most luxuriant in running 

 vpater. Newfoundland and Nova Scotia. — MacKay. River St. Lawrence (1863). — Sir J. 

 W. Dawson. Ottawa River. — H. M. Ami. Elgatches Lake. — Sir J. W. Dan-son. Tuladi Lake, 

 near Lake Temiscouata. — H. M. Ami. Chilukweyuk Lake, British Columbia. — Carter. 

 Nimpkish River, Vancouver Island, British Columbia. — G. M. Dawson. 



