7Q PORIFERA. II. 



genus. The alse of the larger end do not reach so far down along the shaft as in the chelae of the 

 two other subgenera, only to about the middle of the shaft; they bend somewhat forward towards the 

 tooth; together they form almost a triangle, and the}' go in to the shaft with a somewhat indented 

 lower edge. The tooth is elliptical, of about the same length as the alse, but much narrower; it has 

 a long, narrow, downward pointed tuberculum. It is very difficult to get a clear view of the structure 

 of the smaller end on account of the fineness and transparency of the parts. The structure of this 

 end may best be compared with that in A. cHpressiformis, but it is comparatively larger, and the parts 

 are of a somewhat different form. When the chela is viewed from the side, two long, narrow, ridge- 

 shaped bodies that are parallel to each other and run close together are seen at the lower end of the 

 axis. If the chela is turned with the lower end directly towards the beholder, it is seen that the 

 question, as usual, is of alse and tooth, but the optical transverse section does not, as in cupressiformis, 

 form a circle, but on the contrary an ellipsis placed transversely, alse and tooth being nearer to each 

 other and therefore less refolded on the side, where they are separated by a quite narrow slit (PI. XI, 

 fig. 9 h). When the chela is viewed from the front under sufficient magnifying powers, it is seen that 

 the alse form together an almost quadrangular plate, the upper corners are somewhat drawn out, and 

 there is a round incision about to the middle of the ala, which gives to the plate formed by the alse 

 a shield-shaped appearance. The upper edges of the alse continue inward to about the median line 

 of the shaft and form two projections separated from the outdrawu corners by a curve. The tooth is 

 of a similar form as the plate formed by the alse, the upper edge has three teeth, and the upper half 

 of the lateral edges is cut off obliquely. Thus, as in cuprcssiformis, only the lower half of the lateral 

 edges of the alse and tooth is refolded and meets on the side. The drawn-out upper corners of the 

 alse and the mentioned middle projections are directed forward, and when the chela is viewed from 

 the side, they form the forward directed upper part of the hindmost of the two parallel ridges. The 

 tooth has an oblong, somewhat club-shaped tuberculum which is broadest upward. The chela varies 

 somewhat in size, not so much in one individual, but rather considerably in different individuals. 

 Together with the variation as to size we find some variation as to form, as the dimensions of the 

 different parts of the chela may change somewhat. Especially in the smaller chelse the smaller end 

 is comparatively longer and the middle part of the shaft a little shorter. The upper corners of the 

 alse are often more drawn out and together with the middle projections directed more forward. The 

 whole smaller end is at the same time more narrow, and the larger chelse are upon the whole com- 

 paratively more robust than the smaller ones. The chelse occurring in the embryos show new differ- 

 ences, the larger end and especially the tooth being longer, so that the two ends of the chela almost 

 meet. The length of the chelae varies from o-oi8— o-027 mmI ), the greatest breadth varies proportionately 

 from o-oio— o-oi4 mm , and the thickness of the shaft from ca. crooi— o-oo4 mm . Developmental forms of 

 the chela are found rather abundantly, in all stages, from quite fine ones to the fully developed ones. 

 2. Forcipes; these seem always to have the form figured by Levinsen I.e., with one leg crossing 

 the other; they are a little thickened above in the curve, the legs are exceedingly fine, and end in a 

 little knob. The length is about o-ojs" 1 ™, and the thickness of the legs in the middle is less than 



t) When in one individual both large cheke and quite small ones are found, and when chelse are found considerably 

 smaller than the given measures, this is owing to the fact that these chelae belong to the embryos; see below under Embryos. 



