CARCINOLOGICAL STUDIES. 69 



The cephalothorax is, posteriorly, 11 mm. broad and 8^3 

 mm. loog. The specimen of Richters bad about the same size. 



17. G er yon trispin os us Herbst. 

 (PI. 4, fig. 6). 



Cancer trispinosus, Herbst, Krabben und Krebse, Bd. III, Heft 3, 

 p. 43, PI. LVII, fig. 4 (1803). 



Chulaepus trispinosus, Gerstaecker, Carcinologische Beitrilge , in : 

 Archiv f. Naturgeschichte, Jahrg. XXII, 1856, p. 119. 



The Leyden Museum Collection contains one single male 

 specimen of this rare and interesting crab , of which , as 

 far as I know, only one other specimen exists , viz. the 

 original specimen of Herbst's Cancer trispinosus in the Royal 

 Museum of Berlin. Unfortunately the origin of the Leyden 

 Museum crab is quite unknown. Herbst indicates the East- 

 Indies as the habitat of his Cancer trispinosus. The other 

 species of the genus Geri/on occur in the European seas 

 and in the Atlantic Ocean : all are deep-sea forms. It appears, 

 for that reason , very probable to me that Geryon trispinosus 

 Herbst represents this genus in the depths of the indo- 

 pacific seas, and that therefore only two specimens have 

 been collected until to day. 



Gerstaecker created for this species the genus Chalaepus, 

 but it is without any doubt a true representative of the 

 genus Geryon^ established by Kröyer in 1837. Three 

 species of this genus were known up to this date, if 

 we exclude Geryon incertus Miers from the Bermudas, the 

 true place of which is still uncertain : they are Geryon 

 tridens Kröyer from the northern European seas , Geryon 

 quinquedens Smith from the East Coast of the United States, 

 and Geryon longipes A. Milne Edw. from the Mediterranean 

 and North Spanish coasts. 



I have to express my thanks to Dr. Hilgendorf of Berlin, 

 from whom I have received most valuable informations 

 regarding the specimen of Herbst. The latter presents some 

 slight difierences , which are either individual or must be 



Notes from the Leyden Museum, "Vol. XII. 



