KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND. 22. N:0 7. IP, 7 



and rounded, but usually obliquely truncated in front, about the base of the aatenna;. Nearly 

 the whole is covered with hexagoual facets, and tlie pigment constitutes a lai-ge dark- 

 coloured mäss, about half as long as the lieight of the head. The upper antenna? have the 

 base i'ather stout and geniciilated at the second articulation; the part of the base beyond is 

 ciliate on the lower side. The flagella of both pairs of antennas are long and very slender. 

 The abdomen consists of seven segments; but the last three are more or less soldered to- 

 gether, being marked in outline by sutures. Of the three pairs of stylets, the flrst and 

 third extend about equally far backward, while the second pair falls short of this distance. 

 The six posterior legs are slender and subequal, and end in a slender claw; the third and 

 fourth pairs are equally slender and subequal; the first and second are much the smallest. 

 These animals move with very quick motion, with head down, turning över and över.» 



nHyperia, Latreille. The Hyperia; occur principally in the colder temperate and frigid zones. 

 The species have usually a tumid cephalothorax, rounded above; but, in one species, it is 

 much compressed, and rises above to an edge. The four anterior thoracic legs are much 

 shorter than in the others, and the second pair with usually the first, is subprehensile. This 

 prehensile character is produced by a prolongation of the lower apex of the fourth joint, 

 the fifth and sixth constituting the nioveable finger. This finger, exclusive of the claw, or 

 sixth joint, is commonly mucli longer than the process against which is plays; yet the 

 transition appears to be so OTadual to species in which the finger is short, and the hand 

 well formed, that we have doubted the propriety of sustaining the genus Metoecus, of Kröyer, 

 based on this distinction, — that is, on having well-formed hands terminating the second 

 pair of feet. In our Hyperia trigona the legs of the first pair are not at all prehensile, the 

 lower apex of the fourth joint not projecting.» 



From the above it is clear not orily that Dana retained the genus Lestrigonus at 

 the side of Hyperia, but also that he induded in this latter genus the forms now trans- 

 ferred to the genus Parathemisto, A. Boeck. 



Spence Bate was the next author who, in 1862, gave new diagnoses of Hyperia and 

 Lestrigonus, and he suspected that the two genera were only sexually different, as will be 

 seen from the quotation below, but still he retained the latter genus. His diagnoses run: 



»Lestrigonus. Cephalon large, deeper than broad. Pereion short; segments subequal, three times 

 as deep as long. Pleon longer than the pereion; first three segments long and deep; fifth 

 very short. Eyes large, occupying the entire lateral walls of the cephalon. Antennas longer 

 than the cephalon, subequal, having articulate flagella. Mandibles having an appendage. 

 Gnathopoda completely subchelate. Pereiopoda subequal. Pleopoda biramous. Telson 

 squamiform, simple.» 



nHyperia. Cephalon large, deeper than broad. Eyes large, occupying most of the lateral, and 

 encroaching considerably upon the frontal walls of the cephalon. Antennae subequal, short. 

 Gnathopoda subuniform, complexly subchelate, having the carpi produced inferiorly, and 

 forming a process to antagonize with the extremities of the dactyla. Pereiopoda subequal 

 and moderately robust. Three posterior pairs of pleopoda biramous. Telson squamiform. 

 »The separation of Hyperia from Lestrigonus is very doubtful, and depends only upon 

 the length of the flagella of the antenna;; in each genus this is so variable, that it is difficult 

 to say where Lestrigonus ends, and Hyperia commences. In both genera the first articulus 

 consists of several articuli, coalesced together. I have a strong suspicion that they will be 

 found to be sexually rather than generically distinct. They are frequently met with asso- 

 ciated; and I am not aware that a single female of Lestrigonus has been recorded, while all 

 the specimens of which I have been able to detect the sex in Hyperia have been females.» 



The definitions of the genus Hyperia given by the predecessors to Spence Bate, 

 were all too wide as they admitted species belonging to other Hyperiidean genera, 

 but on the other hand the definition given by Spence Bate was too narrow because 

 the characteristic ^Gnathopoda subuniform, com]ilexly subchelate, having the carpi proclueed 



K. St. Vet. Akad. Handl. Band. 22. N:o 7. ^° 



