Natural Ilistory of East Finmarh. 587 



the lower margin of the area ; when this is present it at 

 once determines the species among northern forms. Under 

 favourable conditions, more especially in young incrusting 

 colonies, the lateral margins may be furnished with a pair of 

 spines by the oral opening, or numerous spines all along 

 the margin, but in these cases the basal spine is always the 

 largest and characteristic. When the colony is entirely 

 devoid of spines, it may be distinguished from E. Lacroixii 

 by the lateral margins being smooth, except that their inner 

 edge may be very slightly granulated, but the calcareous 

 posterior portion of the front wall is smooth. 



E. Lacroixii in favoured positions may have a few ex- 

 tremely fine and delicate spines on the lateral margins with 

 the front pair of larger size, or these latter only present 

 (but never the distinctive posterior central spine of E. mono- 

 stachys) . Apart from spines this species may be distinguished 

 from the last by the coarsely granulated character of the 

 entire margins, including the ivhole i^ortion posterior to the 

 membranous area. When present, moreover, the remarkable 

 '^ hollow triangular spaces,'"* scattered often in extraordinary 

 numbers among the zooscia, are at once distinctive. Hiucks 

 wrote of these : " They are not true avicularia, but consist 

 of a three-cornered area inclosed by calcareous walls and 

 covered in by a transparent membrane/' The membrane 

 is frequently destroyed, and they then appear as hollow 

 triangular structures, which bear a general resemblance to a 

 hollow occupied bj'^ a pointed form of avicularium. 



M. Lacroixii and M. monostachys are only provisionally 

 placed in the genus Electra : further observations are 

 necessary to determine their position. In 189^; Levinsen 

 imited the three species Lacroixii, monostachys, and catenu- 

 laria, Jameson, under the last name. M. catenularia is a 

 species which in the boreal and arctic fauna appears to 

 stand quite by itself. It has been placed by McCoy in a 

 genus Pyripora. 



32. Electra pilosa, Linne. 

 Nordky u [Nordgaard) . 



Fam. Calloporidae. 

 Genus Caulokamphus *, gen. nov. 



Front wall entirely membranous, the calcareous border 

 bearing spines. Avicularia stalked and situated among the 

 * Kavkhs, a stalk ; pdfi(})os, a bird's beak. 



