30 F. A. BATHEB, CBINOIDEA <>F GOTLAND. 



angle towards the centre of the <i i|> raore or less truncated. The oiuter margin of 'tlie facet 

 is curved conformably with the ahape of the radial, and a straåght fulcral ridge extends 

 as a chord aeross the curve from the extreme outer eorners of the facet: tliis ridffe is 

 crenelate or slightly toothed. The segment contained l>v the fulcral ridge and the radial 

 are of the circumference is slightly concave and covered with verv fine granules. The tri- 

 angle contained by the fuleral ridge and the lower margins of the radial processes has its 

 inner angle truncated by the curve of the calycal cavity: its floor has a slight triangulär 

 depression on either side and is covered by rather irregular striae tliat continue from the 

 crenelations of the fulcral ridge, paralie] to <>ne another, and at right angles to the ridge. 

 There is no trace of a perforation either on the ridge or towards the inner part of the 

 facet, but there can sometimes be distinguished a slight notch where the facet meeta tlie 

 calycal cavity, and the wall of the cavity on either side of this notch may l>e slightiy 

 raised so as to form two teeth: doubtless the axial cord lay in this notch, and in conrse 

 of evolution the teeth would have met över it, thus forming a perforation. The radial 

 processes are from 0.6 to 0.8 mm. wide at their base in fig. i), where the facet is 2 mm. 

 wide: this may be taken as a typical measurement. Tlie processes are generally of about 

 the same width all the way up, but tend towards a spear-head shape; sometimes they are 

 a little rounded as well, and may then be called petaloid; sometimes, and especially in 

 petaloid forms, the suture-line is depressed, Where the processes enter into tlie wall of the 

 calycal cavity they are slightly hollowed, even though they may be pointed above; but 

 this hollowing is very little if at all greater than the general curvature of the cavity. In 

 the case, however, of the process formed by the lett and right posterior radials, the breadth 

 is greater, the suture lies to the left of the process, the top is truncate, and the side next 

 the calycal cavity is markedly hollowed: the truncated surface is roughened and to it waa 

 attached, probably by close suture, the anal x. 



The calycal cavity passes down to nearly the bottom of the enp, but is constricted 

 a little more than half-way down, as shown in the section (Pl. I, fig. 11). The nature 

 of this constriction is no doubt the same as in P. ollula, where it is better shown 

 (Pl. I, fig. 17). 



The Arms are simple and unbranched. In the type-specimen of P. flagellifer, Ang. 

 (Iconogr. Tal). IV, fig. 1) (Plate I, fig. 1) they are preserved to a length of 3(i mm.: 

 the proximal ossiele is 1.5 mm. high, with its base twiee as wide as its upper edge; in 

 the left anterior radius it has been rubbed so as to appear more square: the next ossiele 

 is also 1.5 mm. high, but the same width all the way up; the third is 2.5 mm. high; the 

 succeeding ones of the same size and then gradually decreasing: the width of the ossicles 

 is abont l.l mm.: the backs of the ossicles are slightly angular, but are a good deal worn. 

 Arms are known in five Englisli speeimens: in one in the British Museum (E 85*2) they 

 are preserved to a length of 14 mm.; the ossicles in this specimen are 4 ram. long and 

 1.2 mm. wide, the height of the cup being 3.8 mm. and its width 4 mm.; in other respecta 

 they are like those öf the Swedish specimen. The venlral side of the arms has not been 

 observed, but a fracture in the specimen figured enables one to see that the section is 

 triangulär with slightly rounded angles, and that there is a large ventral groove from 

 which the axial canal is not yet separated. 



