308 BIOLOGICAL SURVEY OF 



Electriiiidae d'Orbigny, 1851 

 Electra Lamouroux, 1816 



Electra pilosa (Linnaeus), 1766-1768. PL 6, fig. 1. (Os- 

 biirn, 1912, p. 228 {Memhranipora), for synonymy and ref- 

 erences; Whiteaves, 1901, p. 95, for Canadian records.) 

 Rather common at shore stations and occasionally in dredg- 

 ings, especially encrusting algae, more commonly as the nomi- 

 nal form (lent at a with short spines. Taken at eighteen sta- 

 tions. Cosmopolitan. 



This well-known Bryozoan may be distinguished by the 

 absence of avicularia and ooecia and by the presence of long 

 spines about the margin, one of which, below the proximal 

 part of the aperture, is much larger than the others. When 

 growling on flat surfaces, as the fronds of Laminaria, the 

 spines may all be short (form dentata). On small stems or 

 the edges of fronds the spines reach their maximum develop- 

 ment and the central spine especially may occasionally be 

 several times as long as the zooecium. The frontal area of 

 the zooecium below the aperture is conspicuously perforated. 

 The species grows very profusely and colonies are often sev- 

 eral square inches in area. 



Electra monostachys (Busk), 1854. PI. 15, fig. 13. (Os- 

 burn, 1912, p. 227 (Membranipora), for synonymy and ref- 

 erences.) Very abundant in dredgings on hard bottom and 

 occasionally at shore stations, noted at thirty stations. It is 

 a common North Atlantic species and has been recorded sev- 

 eral times from the Arctic Ocean, but apparently it is more 

 common at intermediate temperatures. It appears somewhat 

 strange that earlier authors, Stimpson, Packard, Verrill, and 

 Whiteaves, did not record it, but perhaps it was confused with 

 the following species, which in its branching state it somewhat 

 resembles. 



Usually in form of radiating colonies on shells, stones, and 

 the broader algae. As a rule, it has a single stout median 

 spine and occasionally delicate spines along the lateral border 

 of the aperture. The frontal area of the zooecium below 

 the aperture is usually very minutely punctate, though some- 



