EEPORT ON THE CRINOIDEA. 227 



Although in sections through the lower part of the basal ring the limits of its 

 component joints may be traced by the grouping of the five ligaments referred to above, 

 yet the interbasal sutures do not become clearly visible till the level of the lowest part of 

 the chambered organ is reached. Here they appear as actual gaps in the otherwise 

 continuous network of nucleated connective tissue which forms the organic basis of the 

 skeleton, so that in a stained preparation they are shown as five radiating white lines on 

 a coloured ground (PI. Vllb. fig. 2). They do not, however, reach the outer edge of the 

 section where the connective tissue network forms a complete ring, and this accounts for 

 the absence of any sutural lines upon the exterior of the composite basal piece (PL Vila. 

 fig. 13). The sutural union between this piece and the stem -joints below it appears to 

 be closer than that between the basals and radials, so that the head has a considerable 

 tendency to break away from the stem at the basiradial suture. This was unfortunately 

 the case with one of the two individuals of Bathycrinus gracilis which were met with by 

 the "Porcupine's" dredge in 1869, and the head was consequently not brought to the 

 surface. On the other hand, only the head of Bathycrinus camphellianus is now known 

 (PL VIII. figs. 1, 2. Woodcut, fig. 15 on p. 239), the stem with the basals having separated 

 from it ; while Danielssen and Keren figure an isolated head of Bathycrinns carpenteri 

 which has lost its basals.^ But the most remarkable case of this kind was met with at 

 Station 146, in the Southern Ocean, where the dredge must have passed over a small forest 

 of Bathycrinus aldrichianus. 



About a dozen tolerably perfect individuals were obtained, together with a consider- 

 able number of stems retaining the basal ring at their upper ends. This fact is one of no 

 little importance from the light which it throws on the supposed composition of the 

 calyx in the fossil genus Eugeniacrinus and its allies Phyllocrinus and Tetracrinus. 

 These genera are very common in the Jurassic and Lower Cretaceous rocks, especially of 

 the Continent ; but by far the greater number of calyces which are met with consist of 

 the radials alone, just like that of Bathycmius camphellianus {¥\. VIII. figs. 1, 2), and 

 the family has accordingly been described as distinguished by the absence of basals. 

 De Loriol ^ says, for example, " Le calice est formd de pieces radiales seulement sans pieces 

 basales." Occasionally, however, a calyx is met with still retaining a portion of the stem 

 attached to it. But no sign of sutures is visible in what appears to be its uppermost 

 joint immediately beneath the radials. This joint, with a portion of the stem attached 

 to it below, is also sometimes met with separate from the radials, as in the case of Bathy- 

 crinus aldrichianus and Bathycrinus gracilis. But the absence of sutures, as shown by 

 the condition of an adult Batlujcrinus, is no proof that the piece in question does not 

 consist of a ring of closely united basals, a point as to which I have no doubt whatever.^ 



The fibres which efi"ect the synostosis of the basals with the radials above them are 



1 Nyt 3Iag.f. Nccitirvidenslc, Bd. xxiii. Tab. i. fig. 6. - Paleont. Franj., loc. cit., p. 74. 



3 Ann. and Mag. Nat. Hist., 1883, ser. 5, vol. xi. pp. 327-334. 



