vol. 



18'J 



8'J3^''] rR(;)CEi<:DiNGS of the national museum. 159 



pcaraiice of being po^iched, the poiiclies perhaps corres]M)n(liii,!^ to ver- 

 ruca". Below this thin region the muscle pro(;esses are somewhat 

 longer than further down, suggesting a second sphincter. 



The disc is very broad, measuring G"" in diameter. Its whole sur- 

 face, with the exception of a small area immediately surrounding the 

 mouth, is covered with tentacles, or with oiienings which correspond 

 to them. The tentacles must have been exceedingly numerous when 

 all were present, having been arranged in as nmny as fourteen or fif- 

 teen cycles. They are sliort, very sliort, wlien compared Avith those of 

 B. tuediw, those of the inner cycles, a few of Avhich persist in the 

 large specimen, measuring only l.C*"'" in lengtli. In other respects, 

 however, they have all the characteristics ot the Bolocerid tentacles. 

 They are attached to the disc by a narrow neck, the mesoglcea of which 

 is very thin. They arc readily deciduoiis and they are fluted. In 

 character they resemble the tentacles of />'. ixmnosa rather than B, 

 tu€di(v, being somewhat fltjccid. Above the neck of the tentacle there 

 is a sphincter-bearing fold of mesoghea, projecting into the cavity of 

 the tentacle, as in other Bolocerids. 



The mouth is slightly jirominent and two well developed siphouo- 

 glyphes are present. It is diflicult to estimate the number of mesen- 

 teries j)resent. I jiulge that there are about forty-eight pairs of perfect 

 mesenteries. Between each ])air of perfect mesenteries there are three 

 well detined series of mesenteries of gradually diminishing size and be- 

 longing to three different cycles, so that if the estimate of forty eight 

 is correct for the first cycle, there will l)e in all three hundred and 

 eight four i^airs of mesenteries, arranged in four regulai' cycles. This 

 number does not, however, at all comparewiththenumber of tentacles, 

 and if the column wall be closely examined a. number of minute ridges 

 may be seen between the jtaiis of nn'senteries, liardly, if at all, rising 

 above the level of the endoderm, and not apparently arranged in regular 

 pairs or separable into detinite cycles. These seem to be somewhat 

 irregularly formed abortive (or incipient ?) mesenteries, an attempt be- 

 ing api)arently made to i)reserve the relation of mesenteries to tenta- 

 cles which is usually found. 



The specimens examined show no trace of reproductive organs, but 

 from the general appearance of the mesenteries it is presumable that 

 the ova or spermatozoa are borne by the imperfect mesenteries of the 

 second, third, and fourth cycles. 



The nnisculatnre of the mesenteries is weak and presents no such i)e- 

 culiar appearance as has been described for B. pannosa. The muscles 

 on the emloc(elic face, however, appear to be transverse in the region 

 near the column wall, bnt form a low and diffuse longitndimil muscle 

 pennon covering the inner three-quarters of the muscle bearing region 

 of the mesentery (PI. xxiii, Fig. 33). The parieto-basilar nniscle is 

 present (PI. xxiii. Fig. 32), as sliown by the direction of its fibres, 

 but it produces no such cavities in the mesogla'a of the region of mes- 



