STAUKOCALYPTÜS PLEORHAPHIDES. 227 



roughness first sets in as an extension of that at the ends of the 

 paratangentials ; thence it proceeds to develop towards the spicular 

 center and from this point proximad for a short distance on the 

 shaft. Kot that the roughness develops on all the old pentactins 

 before these are protruded as prostalia. Of those which already 

 stand out and form the gossamer-like covering on the exterior, 

 many indeed have the rays roughened in the manner described; but 

 in certain others these are perfectly smooth exce})t subterminally. 

 It is difficult to say if all the latter will eventually acquire the 

 character of the former. 



Kunuing along with hypodermally situated paratangentials 

 are occasionally seen some fine diactins, which thus help to sup- 

 j^ort the dermal layer. 



The dermalia (PL XVI., figs. 3-5) are rough diactins. 

 Exceptionally they may be stauractins or tauactins ; extremely 

 rarely, orthodiactins and monactins. 



The diactins measure 264-520 a (on an average, 400 n) in 

 total length and about 9? « in thickness at the middle. They 

 are generally gently bent in a bow-like mannei", the concavity 

 facing downw^ards. They taper slightly tow^ards both ends which 

 are either rounded or conically but bluntly pointed. The center 

 is usually without an external swelling ; only occasionally it is 

 marked by a pair of opposite bosses and much less frequently 

 by a single unilateral boss. 



A noteworthy feature of the present species consists in the fact 

 that the (jastraUa are represented by straight diactins. I at first 

 felt inclined to pass over the matter by simply assuming a total 

 absence of gastralia for the species. Upon further studies, how- 



