126 G Canadian Arctic Expedition, 1913-1918 



This genus seems closely related to Peachia Gosse, especially to P. triphifUa, 

 which has a three-lobed conchula. But that was not the typical species. The 

 earlier described species, L. hastata, must be laken as the type of Peachia. 

 That species has a far more complicated conch ula, but its mesenteries are arranged 

 in essentially the same way, though the longitudinal mesenterial muscles are 

 very different in form, being recurved, much wider and not so thick, and 

 pinnate instead of reniform or crescent shaped as in our species. 



Both have two cycles of mesenteries, those of the second cycle being un- 

 developed in the sulcular lateral exocceles, so that there are but 10 pairs of mesen- 

 teries in each genus. But the arrangement is strictly hcxamerous. The failure 

 to develop two pairs of mesenteries of the second cycle does not change the 

 regular hexamerous condition of the six primary perfect pairs. 



The only external character for the separation of Bicidiopsis from Peachia 

 that can now be relied upon is the great difference in the conchula. 



In P. hastata the conchula is described and figured by Gosse (Actin. Brit- 

 anica) as very large, consisting of two large rounded lobes, bearing 12 to 20 

 processes, more or less divided, and therefore very different from that of our 

 species. He states positively that it has a basal pore, as in our speci< s. 



McMurrich failed to find a terminal pore in preserved specimens that he 

 described under the name Peachia quinquecapitata, from Nanoose bay, Van- 

 couver Island, in 15 to 25 fathoms (op. cit., 1913). Probably the pore was 

 tightly closed in his specimens. His species belongs to Bicidiopsis, as here 

 defined. 



Andres described a species, evidently of this genus, under the name Siphon- 

 actinia tricapitata, but having only three papilliform processes on the conchula. 

 One of his specimens had 18 tentacles; the other two had 12 tentacles each. 

 He did not describe its internal structure but gave a good coloured figure. 

 It closely resembles B. tubicola in form and colour. It should be called Bici- 

 diopsis tricapitata. 



I have separated this genus from Siphonactinia on account of the presence 

 of 20 mesenteries, instead of 12; and because of the more elaborate conchula, 

 which carries a group of papilliform lobules, not found in that genus. 



Bicidiopsis tubicola. New species. 

 Plate XX; Figure 1. 



The following description was made from two living specimens taken by me 

 in the harbour of Eastport, Maine, at low water mark of a very low tide, 

 burrowing in sand and gravel, up to the tentacles. 



The body of the larger specimen in partial expansion was nearly cylindrical, 

 about three times longer than broad, obtusely rounded and perforated at the 

 base, without a basal disk. The body-walls are salmon-colour and somewhat 

 translucent, allowing the mesenteries to show through as whitish lines. The 

 intervals between these lines are swollen and transversely corrugated by wrinkles; 

 posteriorly the surface appears somewhat reticulated by wrinkles, enclosing 

 polygonal areas. No suckers are ordinarily visible, but the creature can adhere 

 to the side of a glass dish by the surface of the body, indicating the presence of 

 minute or retractile suckers; minute round pits, which may be contracted 

 suckers, are often visible with a lens on the preserved specimens. 



Tentacles twelve, large, stout, tapering, but usually obtusely pointed. 

 Their colour is pale salmon, brown at the inner base, and crossed by four bands 

 of light brown. The disk is small, brownish around the mouth, outside of this 

 it has a circle of pale salmon, and is then brownish at the bases of the tentacles. 

 The mouth is salmon-colour inside. It is furnished with a large, prominent, 



