REPORT ON THE MONAXONIDA. 



XIX 



shown in the figure. Usually, at any rate, the spicule is more or less contort, the two 

 hooks lying in two diflferent planes. 



4. Chelse (woodcuts, Fig. V., 5, 6, and Fig. VI.); these are the most complex of all 

 the microsclera, and present us mth a considerable range of variation in detail. The 

 fundamental shape will be best understood from the accompanying figures, so we 

 shall make the description short. 



It will be seen that each spicule consists of a more or less curved " shaft " (.s), 

 bearing at each end a variable number of sharply recurved processes {at, at' , It, It') 

 which may be conveniently spoken of as the •'' teeth," 

 or, when they are broad and much expanded, the 

 "jaalms." Each tooth or palm is connected with the 

 shaft by a buttress-like projection of the latter, called 

 by Mr. Carter-^ the " falx," and generally itseK con- 

 sists of a thin, flattened, oval lamella, so transparent 

 as to be very difficult to make out. The terminal 

 portion of the falx, upon which the tooth or palm 

 directly rests, has been called by Mr. Carter the 

 " tubercle " {t, t'); it is generally very conspicuous 

 through the transparent lamella. Very commonly 

 there is a single central or anterior tooth [at, at'), 

 and two lateral teeth {It, It') placed one on each side 

 of it. When the teeth are comparatively narrow and 

 the two lateral teeth are completely cut away from the 

 shaft, as in Fig. VI., 1, la, the spicule is said to be 

 " tridentate;" when, however, they are broad (forming 

 palms) and the lateral palms remain adherent to the 

 shaft for their entire length, the central palm alone being completely separated, 

 as in Fig. VI., 2, 2a, the spicule is said to be " palmate." Numberless gradations exist 

 between these two types, depending upon the extent to which the incisions between the 

 lateral teeth and the shaft are carried, and upon the breadth of the teeth or palms. The 

 distinction between the two types is, as has already been pointed out, a purely 

 artificial one, but for the sake of convenience it may be retained. In some species 

 {e.g., Chondrocladia concrescens (?)) there may be as many as seven teeth completely cut 

 away from the shaft and from one another (PL XXI. fig. 12), while in one species 

 {Sideroderma navicelligerum) there is a very remarkable little chela (PI. IX. fig. 8) in 

 which there is only a single (the median) tooth at each end. The shaft itself is frequently 

 expanded laterally into wing-like processes, or fimbriae (woodcut, Fig. VI.,/), which may 

 extend along its whole length, but are more generally confined to one (or the two) ends. 



1 Ann. and. May. Nat. Hist., ser. 4, vol. xiv. pp. 208, 209. 



Fig. 



VI. — Structure of the chelae. 1, tridentate 

 anisochela, front \-iew ; 1«, .same, side view ; 2, 

 palmate isochela, front view ; 2a, same, side view ; 

 t, t', tubercle; at, at', anterior tooth or palm; It, It, 

 lateral tooth or palm ; s, shaft ; /, fimbria. 



