's RIJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN. 



93 



Carapace with 2 teeth in the middle line before the cervical 

 groove and with 2 minute teeth, situated abreast, between the 

 posterior tooth and that groove. Outer margin of proximal (outer) 

 antennal squame with two sharp teeth, of the 5 teeth on the inner 

 margin the first is much larger than the following. 



Length, outer antennae included, 25,5 mm. bicuspidatus (de Man). 



When working at the Scyllaridae in 1915 I was enabled to study 

 two young specimens of ScylL arctus (L.) from the Gulf of Naples, be- 

 longing to the Leyden Museum (J. Gr. de Man, 1. c. p. 84), a male long 

 54 mm. and a female long 34 mm., the outer antennae included. I had 

 asked for specimens of Scyll. arctus of small size, in order to compare 

 them with Scyll. bicuspidatus, of which the single specimen collected was 

 25,5 mm. long. I had not succeeded in finding a description of Scyll. 

 arctus (L.), in which the notch at the anterior extremity of the sternum 

 was described and a full-grown specimen was then not at my disposal. 

 These two specimens are now again lying before me together with a 

 fullgrown ova-bearing female from the Gulf of Naples long 125 mm., an 

 adult male from Kovigno long 115 mm. and three somewhat younger 

 specimens from the Mediterranean. The notch at the anterior extremity 

 of the sternum appears in the larger one of the two specimens, examined 

 in 1915, semicircular with a minute incision in the middle line, the depth 

 being nearly already the same as in the adult (Fig. 1), but in the spe- 

 cimen, long 34 mm., the notch (Fig. 2) is much less deep and almost 

 fully resembles that of Scyll. bicuspidatus (J. Gf. de Man, 1. c. fig. 12a). 



Fig. 1. Scyllarus arctus (L.) 



(J! 115 mm. long, outer 

 antennae included. Rovigno. 



Fig. 2. Scyllants arctus (L.) 



young female, 34 mm. long, 



outer antennae included. Mediterranean. 



It is now evident that in 1915 the notch in the younger specimen, long 

 34 mm., has erroneously been considered by me as the normal form in 

 this species, while the shape of the notch, presented by the other, long 



54 mm., was regarded by me as abnormal 



an incomprehensible 



