338 ME. HENET B. BIGELOW— BISCATAJST PLANKTON : 



Nectopyramis thetis, are contained in the ' Albatross ' Eastern Pacific Expedition ; and 

 in my report on that collection, now in press, tliey are more fully described and figured, 

 and questions of synonymy and classification are discussed in greater detail than the 

 scope of the present paper allows. 



In conclusion, I may say that the excellent condition of the specimens, upon which 

 Dr. Fowler is to be congratulated, have made their study much easier than is usually 

 the case with preserved Siphonophores. 



CALYCOPHORJ^. 



MONOPHYID^, Claus, 1874 



Sph^ronectin.^ (Huxley, 1859), Haeckel, 1888. 



Nectopyramis, gen. nov. 



A single nectophore, apparently a monophyid, differs in so many important features 

 from all known Calycophorae that it has been made the type of a new genus. Necto- 

 pyramis is also represented in the ' Albatross ' collection by a considerable series. When 

 I first examined the specimen I thought, from the appendages, that it might prove to 

 be tbe polygastric state of the eudoxid described by Chun (1888, 1897 ^'), Bedot (1904), 

 and Lens and Van Eiemsdijk (1908) as Cemtocymba. But the bract, though in some 

 respects suggesting that form, differs so much fromjt in the structure of its somatocyst 

 as to forbid the union. And I may forestall my account of the ' Albatross ' collection 

 by adding that it shows strong evidence connecting Ceratocymha Avith Ahyla leuckartii, 

 a union the possibility of which has already been suggested by K. C. Schneider (1898). 



So far as we can judge from the single available example, Nectopyramis may be 

 detined as Monophyidce with rounded nectophore, tclth the somatocyst represented by a 

 series of divergent canals : the cormidia are loithout special nectophores. 



Nectopyramis thetis, sp. nov. (PI. 28. figs. 1-4.) 



Occurrence : 300 to fathoms. 3G k. 1 specimen in excellent condition. 



Nectophore. — The nectophore, which is 11 mm. in greatest length, is of a pyramidal 

 form, so characteristic that it makes the animal noticeable at the first glance. It may 

 be described as bounded by four equilateral triangles, with somewhat concave margins ; 

 but these triangles are hardly comparable to the facets of the cymbonectids or diphyids, 

 because they join each other by gradual curves, instead of being separated by sharp 

 ridges. In this regard, then, the general form is intermediate between that of such 

 forms as Sphceronectes and Ualopyramis. The gelatinous substance of the nectophore 

 is stiff, but almost perfectly transparent. 



The nectosac lies in one of the triangular faces, near its dorsal angles. It is 

 comparatively small, shallow, and saucer-shaped, and its subumbrellar surface, though 

 torn, is sufficiently well preserved in places to show that its musculature, like that of 

 Rippopodius, is so weak that it cannot serve as a very effective swimming-organ. The 

 hydrcBcium is large, deep, and laterally compressed. It is situated immediately above 

 the nectosac. Its opening lies along the line of junction between two of the facets, and 



