— i6 — 



b. Carapace with a well developed cervical groove. 

 Sixth abdominal segment shorter than the fifth. 



This group comprises only two species, viz. T. cor- 

 nuta lllig and T. egregia H. J. H. 



For reasons given above T. elongata Guer., T. mega- 

 lops lllig, T. Agassi\ii Ortm. and Parathysanopoda folii- 

 fera lllig are cancelled or reduced to synonyms ; all other 

 synonyms are given in the « Siboga » report, which 

 besides contains remarks on or descriptions of all species 

 of the genus excepting T. pectinata Ortm., T. cornuta lllig 

 and T. egregia H.J. H. These three species have been 

 described in Nos. 3o and 42 of this Bulletin ; and T.insig- 

 nis H. J. H. is identical with T. cornuta lllig, but the 

 later name must be applied, as it has a priority of about 

 four days. 



It may be added that while T. microphthalma G. O. S. 

 and T. acutifrons Holt and Tatt. are known only from v the 

 northern Atlantic, I have seen specimens at least both 

 from the Atlantic and the Pacific of the nine other species. 



Meganyctiphanes Holt and Tatt. 



To the generic differences between this genus and 

 Nyctiphanes G. O. S. pointed out by Holt and Tattersall 

 may be added the excellent characters afforded by the 

 copulatory organs. In Meganyctiphanes these organs are 

 essentially as in Thysanapoda ; the inner lobe is short with 

 its three processes well developed as in this genus, and the 

 median lobe has not only a good-sized lateral process but 

 besides additional processes (in a specimen investigated 

 even four small additional processes). In Nyctiphanes the 

 inner lobe is quite peculiar, being extremely produced in 

 an oblong, more or less triangular, large plate with the 

 outer margin sinuate and its major part serrate, while the 

 spine-shaped process is developed as a curved, slender spine 



