TRANSACTIONS OF THE SECTIONS. 133 



corals of the pala?ozoie roclcs, to wliidi it corresponds in tlie nuiuerlcal law of its 

 body-segments/and of whicli it uiiylit, in some respects, be regarded as a living nou- 

 coraligenous representative. 



On the Structure of Cyphonautes. B)/ Prof. Allman, FM.S. 



This remarkable little organism, whose structure and ultimate destination have 

 been variously described by ditl'ereut observers, was obtained by the author in 

 considerable abundance in Moray Firth. The animal is enveloped in a mantle, 

 and the whole enclosed in a delicate, transparent, structureless test formed by two 

 valve-lilio triangular plates, which are in contact along two edges, and separated 

 from one another by a narrov/ internal along the third. Its form is thus that of a 

 very much compressed pyramid. The author distinguishes by the term base the 

 broader edge where the two plates of the test are separated' from one another, 

 while the other two edges are distinguished as the anal and abanal edges. The 

 apex is the angle opposite to the base ; and here a narrow passage exists, throu"-h 

 vvhich the fleshy vralls of the mantle are brought into immediate contact with the 

 surrounding water. 



In the base are two largo oval openings, one (the larger) situated towards the 

 anal edge, and the other towards the abanal. The former leads directly into the 

 cavity of the mantle ; its edges are prolonged by a hollow membranous lobe, 

 ciliated on its margin, and uninterruptedly continued round the anal side of the 

 opening, but deficient on tlie opposite side. 



A largo part of the mantle-cavity is occupied by the pharynx, a spacious thin- 

 walled sac, which opens into the mantle-cavity by a long curved somewhat 

 S-shaped slit with thickened and ciliated margins, which at one side are continued, 

 in the form of two short ciliated tentacles, beyond the large opening situated near 

 the anal side of the base. Towards the apex the pharynx becomes suddenly narrow, 

 and is here lined by vibratile cilia, and marked by circular striiB which possibly 

 indicate the presence of sphincter fibres. It now "turns towards tlie anal side, and 

 then bends downwards towards the base and enters a tliick-walled snbcylindrical 

 stomach. This runs towards the base parallel to and a little within the "anal edge 

 of the test, and is ultimately continued into a short straight intestine, which ter- 

 minates by an anal orifice in the mantle-cavity near the outer opening of the latter. 

 From the upper part of the walls of the pharynx a narrow bundle of fibres passes 

 to the ape.x of the mantle-cavit}'. 



Upon each side of the pharynx, and lying against the stomach and intestine, is a 

 large oval mass. Its situation would suggest the probability of its being an hepatic 

 organ ; but it is altogether so enigmatical that it would be rash, with'oiu' present 

 knowledge of it, to insist on assigning to it any special significance. 



In contact with each of these enigmatical organs is a small tubercle, from which 

 a bundle of short fibres pass ofi' in a radiating direction. The resemblance of these 

 bodies to a pair of nervous ganglia is obvious; but the author was more inclined to 

 regard them with Schneider as indicating points of attachment of the contained 

 animal to the two calves of the test. 



The smaller of the two openings in the base (that, namely, which is situated 

 near the abanal edge of the animal) is, like the other, surrounded by a hollow 

 membranous _ lobe with ciliated margin; this is uninterruptedly continued round 

 the abanal side of the opening, but is deficient on the opposite side. The openini^ 

 leads into a special chamber entirely shut off from the cavity of the mantle and 

 from_ the pharynx. The walls of "the chamber are lined v\dth cilia, and it has 

 within it, or in immediate connexion with its walls, two peculiar structures. One 

 . of these is a somewhat pyriform organ, which, with the narrow end close to the 

 orifice of the chamber, extends from this point into its cavity ; it is composed of 

 a ms.<:s of spherical bodies. Tlie other extends over the roof of the chamber in 

 form of a cap : it consists of two portions, one of which lies directly on the 

 walls of the roof and has a transversely laminated structure, which, however, dis- 

 appears towards the abanal side of the 'chamber ; the other is an oval mass of' glo- 

 bular cell-like bodies, and lies on the free convex surface of the laminated portion. 



Flere, again, this part of the Cyphonautes is iu the highest degree enigmatical • 



