84 CAKL BOVALLIUS, AMPHIPODA HYPERIIDEA. I. 2. HYPERIID^E. 



gitus posterior. Primus pollicis articulus (v. qvintus pedis) magnus, conicus; secundus 

 ungvis est pusillus. Digitus conicus, pollice aliqvantillum brevior. Margo utriusqve 

 pollicis articuli posterior, margoqve digiti anterior per totara longitudineni serrati. Cetera 

 cum genere Hyperia ferme conveniunt». 



From the characteristic »manuqve armati cheliformi» and "digitus conicus, pollice 

 aliqvantillum brevior», it is clear that Kroeyer was quite right in generically separating the 

 animals thus characterised from the old genera Hyperia, Latreille, and its synonym Lestri- 

 gonus, H. Milne Edwards, which have the first two pairs of perceopoda subcheliform, not 

 cheliform, with the carpal process more or less produced, and the carpal process of the first 

 pair constantly less produced than that of the second pair, or not produced. But as the 

 true character of these carpal processes in Metoecus, or Hyperoche, and in Hyperia had not 

 been more closely examined, and the different building of them thus made out, the identity 

 of the genera was once and again claimed by subsequent authors owing to the supposition 

 that the development of the carpal processes might be gradual and thus the limit between 

 the genera impossible to fix. Spence Bate in 1862, Spence Bate and Westwood in 

 1868, and myself in 1885, pronounced this opinion. Later I had the opportunity to make 

 a more careful investigation in the matter and found that the carpal processes in Hy- 

 peroche were compressed, almost knife-shaped but that in Hyperia they were broadly 

 hollowed, spoon-shaped and that in other representatives of the family Hyperiida?, com- 

 monly looked upon as distinct genera, the same characteristic reappeared, thus for in- 

 stance showed Euthemisto and Parathemisto a narrowly hollowed, gauge-shaped carpal 

 process in the second pair of perasopoda, but Phronimopsis a compressed, bluntly knife- 

 shaped, analogue process. 



Kroeyer regarded his type as identical with Oniscus medusarum, of 0. Fabricius 1 ), 

 and claimed the name Metoecus medusarum for it, thus applying on his species the specific 

 name given in 1776 by 0. F. Muller 2 ) to the typical specimen described and figured in 

 1762 by Strom. 3 ) It is to be observed that both the description given by Str0m and 

 the name Cancer medusarum, 0. F. Muller, were quoted by 0. Fabricius 1. c. as syno- 

 nyms for his Oniscus medusarum. The question if Oniscus medusarum, 0. Fabricius 

 and Cancer medusarum 0. F. Muller really are identical will be treated below, under 

 Hyperia medusarum; here it is sufficient to say that the wording of the diagnoses evidently 

 shows that none of them has anything to do with Kroeyer's species, thus the specific 

 name medusarum was wrongly used by Kr0yer, who ought to have given his species a 

 new name. 



H. Milne Edwards in 1840 and Dana in 1852 mentioned the genus Metoecus, 

 with the characteristics assigned by Kroeyer. A. White gave in 1857, 1. c. p. 207 the 

 following diagnosis for the genus Metoecus, Kroeyer: »Two first pairs of legs much shorter 

 than the following, and ending in a little two-toed claw, the movable finger of which has 

 at the end a little rudimentary nail». Spence Bate in 1862, as noticed above, united it 

 with Hyperia. In 1870 A. Boeck restituted Metoecus as a genus by itself. When he in 



') Fauna Groeulandica. Copenhagen and Leipzic, 1780, p. 257. 



2 ) Zoologue Danicse Prodroraus. Copenhagen, 1776, p. 196. 



3 ) Physisk og Oeconomisk Beskrivelse over Fogderiet S0iulm0i\ Vol. 1, p. 188, 4:to, Sore, 1762. 



