182 LIVERPOOL BIOLOGICAL SOCIETY. 
2. Gastrosaccus sanctus (Van Beneden, Recherches sur 
la Faune Littorale de Belgique, 1861—non Norman Rep. 
Brit. Association, 1868). 
A few small specimens not exceeding 4 mm. in length, 
and therefore probably young, as Sars (Middelhav. Mysider, 
p. 65) gives 13 mm. as the length of the adult female. 
In this species a portion of the hind margin of the cara- 
pace on each side of the median line is raised in the form 
of a tooth projecting forward. Sars (1. c. p. 72) says that 
the species described under the above name by Norman 
(l. c. supra) is a distinct species, being described as having 
“the fifth segment of the pleon produced backwards on 
the back into a well developed spine,’ which is not the 
case in Van Beneden’s species. This also applies to the 
earlier described Mysis spimfera of Goes (Crust. Decapoda 
Podopth. Marina Suecice, 1863), to which Norman’s species 
ought probably to be referred. I may add that Norman 
does not mention the curious tooth-like appendages above 
mentioned. I find that the smaller the specimen the fewer 
are the spines on the sides of the telson. 
