— 23 — 



months ago Holt & Tâttersall established a new species, T. acu- 

 tifrons ; the study of their typical spécimens kindly lent me 

 gives the resuit that some of them are immature spécimens of 

 the species formerly referred by me to T. pectinata, while two 

 others of them are adult or subadult spécimens of T. distin- 

 guenda, H. J. H. I will now give a description of the front part 

 of carapace and the lobe from first antennular lobe in T. acuti- 

 frons for comparison with the following description of the real 

 T. pectinata Ortm., and besides some remarks on the diffé- 

 rences between T. acutifrons and T. distinguenda. 



In nearly full-grown or adult spécimens of T. acutifrons 

 the front part of carapace constitutes, seen from above, a rather 

 low triangle : the most proximal part of its latéral margin is 

 slightly concave, the distal part slightly convex, the distal angle 

 measures iio°-i2o° and terminâtes in a tiny tooth directed 

 upwards or obliquely upwards and forwards. In spécimens 

 being only half-grown or little more than half-grown the triangle 

 mentioned is a little longer, the distal part of its latéral margins 

 is straight, the terminal angle measures only about 90 0 or rarely 

 about 100 0 , and the tip is sometimes produced into a tiny 

 process directed essentially forwards; in still smaller spécimens 

 the triangle is still longer, the terminal angle 85°-8o°, and the 

 tip more produced as a tiny subhorizontal process. The upper 

 surface of the front part of the carapace is shaped essentially as 

 in T. vulgaris and T. œqualis, but the mesial keel is higher at 

 the dorsal organ. The eyes are rather small, brown. The lobe 

 from first antennular joint is, seen from above, oblong, longer 

 than broad, rather small, occupying slightly more than the 

 inner third of the proximal part of the upper surface of second 

 joint; its outer margin is nearly parallel with the mesial line, 

 while the distal portion of its inner margin is directed obliquely 

 outwards; it terminâtes in a short acute process which, seen 

 from the side (fig. 12 in my former paper), is triangular and in 

 rather large or adult spécimens shorter than deep, in about 

 half-grown or still smaller spécimens sometimes about as long 

 as deep. From the inner oblique margin of the lobe the stiff 

 coupling setas (described in my former paper) proceed. A broad, 



(42) 



