424 DR F. A. BATHER. 



bearing marginal 6 at the ball of the foot. Since the foot-half is not so extended, 

 the angle or curve between leg and toe is quite short, but at the toe-end of this curve 

 is a marginal with an obtuse outer angle or blunt point, corresponding in position to 

 the toe-spine. In general form the lower half of the frame in Ceratocystis Perneri 

 resembles that of Cothurnoci/stis curvata rather than C. Elizae. 



§ 257. The stem of Ceratocystis comprises three regions, precisely comparable with 

 those in Cothurnocystis, though each region differs slightly in construction. The 

 nature of the difference, put broadly, is that Ceratocystis shows more signs of what I 

 believe to be the original small plates that enclosed the stem-lumen. Thus, the 

 plates of the proximal region apparently were more than four pairs of dimeres, and 

 resemble imbricating scales ; the conical lumen of the median region was also surrounded 

 by small plates imbricating distalwards, and firmly united only at their inner ends ; the 

 distal region appears in many specimens to have been composed of cylindrical columnals, 

 but closer examination shows that these also, at least in the upper part of the region, 

 retain on their outer surface traces of the original imbricating plates (the " seitliche 

 Anhangsorgane " of Jaekel's description). Dr Jaekel describes the columnals of this 

 region as " zweizeilig," i.e. composed of dimeres ; it is possible, but I cannot confirm the 

 statement ; probably there was some variation in the extent to which the original 

 elements were united, 



§ 258. This analysis will have shown how close is the fundamental resemblance of 

 Ceratocystis to Cothurnocystis, and one might even find other points, such as the greater 

 swelling of the marginals on one face. But the interpretation of the internal anatomy 

 given by Dr Jaekel involves important differences. He places the mouth between the 

 two processes of the leg, and regards the concavity above the instep as an anal opening. 

 It is, however, clear that, if there be any reality in the above comparison of Ceratocystis 

 with Cothurnocystis, then the vent must have lain where Jaekel places the mouth. 1 

 can find no trace of any structures that resemble anal plates or valves, but the small 

 square marginal in this position may perhaps be homologised with the somewhat similar 

 plate over which the vent passes in Trochocystis. If there were any opening into the 

 thecal cavity at the place where Jaekel puts the anus, then that opening would, for 

 the same reasons, be the intake and not the vent. Comparison with Cothurnocystis, 

 however, suggests that the excavation in this region is nothing but the angle of the 

 instep, and that the intake must be looked for nearei" the stem. It is in fact the case 

 that, among the individuals of Ceratocystis examined by me, those lying in the same 

 position as a Cothurnocystis, with the obverse face exposed, show on that face definite 

 folds or notches along the inner edge of some lower marginals. These are best seen in 

 El 6074 (text-fig. 35), but their presence has been proved in other specimens, and I can 

 only explain them as indications of a subvective system. In the absence of a far greater 

 amount of material I hesitate to express any decided opinion as to the precise structure 

 of that system in Ceratocystis ; but the general argument from comparative anatomy 

 convinces me that the relative positions of intake and vent are as suggested here. 



