e 



mm. 



one of Abylopsis qtiincunx. To be absolutely sure that we had taken the right nectophores, w 

 detached them from complete specimens, the complete Abylopsis gicincunx measuring 6 

 and the Abyla pentagona 23 mm. We found even some complete specimens of Abyla pentagona 

 of greater length, but they happened not to be well-preserved enough. 



The relative size of superior to inferior nectophore is in both species very different. 

 The inferior one of Abylopsis qjiinauix is only a little larger (about i7i,) and the inferior 

 one of Abyla is 4V. times longer than the superior nectophore. This is shown clearly in Chux's 

 figure 97 b of Abylopsis qtiinctinx. 



This of course makes the outward appearance totally different. 



Comparing (PL II, figg. 17, 18, 19 with PI. Ill, figg. 24, 25, 26) the superior nectophores 

 of the two we find that there is no difference in structure as far as the facets are concerned 

 First of all the ridges of Abylopsis are serrated, especially the ridges of the anterior facet. 

 In Abyla there are only remains of serrating in the four ridges which form the apertures of 

 the hydroecial canal. 



The upper nectophores of both Abyla and Abylopsis are four-sided and have two parallel, 

 pentagonal facets, an anterior and a posterior one. This anterior facet in Abylopsis (PI. Ill 

 fig. 24) is an almost regular pentagon, the basal ridge being somewhat shorter and curved, 

 whilst in Abyla (PL II, fig. 17) the same ridges differ in length; the upper ridges are shorter, 

 and the angles which they form with the longer basal ridges of the pentao-on are less acute. 

 The basal ridge is only a little convex and much smaller. The ventral facet shows some 

 difference too. In Abylopsis (PL III, fig. 25) and in Abyla (PL II, fig. 18) the upper rido-es 

 have the same course, but whilst in Abylopsis the postero-lateral ridges are straight and beo-in 

 to bend only at the ver)- distal end abruptly to form the teeth of the hydroecial canal the 

 same ridges in Abyla (PL II, fig. 18) are convex and meet each other gradually. The teeth 

 of the hydroecial canal are less sharp and the basal transverse ridge is less emaro-inate than 

 in Abylopsis. 



Naturally the differences between the posterior and anterior facets cause dissimilarity in 

 structure of the lateral facets. The two superior lateral facets in Abylopsis (PL III, fia. 26) form 

 a regular quadrangle; in Abyla (PL II, fig. 19) there are 4 ridges too, but the superior one 

 (the ridge which connects the superior angles of anterior and posterior facet) is smaller than 

 the inferior one, moreover the latter is curved. This includes a deviation of the lateral rido-es 

 and an irregular aspect of the whole. 



The infero-lateral ridges are in Abylopsis and Abyla four-sided, and are produced inferiorly 

 into the lateral wall of the hydroecium. In Abylopsis (PL III, fig. 26) the ano-Jes are more acute 

 the teeth of the hydroecium are long. In Abyla (PL II, fig. 19) the angles are blunt and the 

 teeth shorter. The posterior wall of the hydroecium is formed by the posterior facet, the anterior 

 one b)- a single facet, four-sided, the basal ridge of which is deeply emarginate and serrated. 

 Concluding we may say that the great difference between the superior nectophores of Abyla 

 and Abylopsis is that in Abylopsis all angles are acute, in Abyla all blunt. The interior 

 (phyllocyst, nectosac, canals of the nectosac and hydroecium) do not show any dissimilarity to 

 those in Abyla pentagona. 



