Prof. T. Thorell on the 



2. Lateral teeth of the palp-fingers form, both on the inner and outer 

 side, a row of teeth placed two and two transversely near to 

 each other. (The tooth under the sting is sometimes wanting.) 



TiTYus, (C. L.Koch), 1836. 

 Type T. Kneatus, C. L, Koch, 1845. 



Liferi or margin of the immovable mandibular finger armed with one 

 (very small) tooth. (A tooth or spine under the sting is rarely 

 wanting.) 



* Both the inner and the outer lateral teeth of the palp-fingers 

 aiTanged in a single row. 



1. Thefit'thcaudal joint broadly excavated above, its upper margins 



forming an elevated keel. (The tail gradually somewhat in- 

 crassated from the vicinity of the base to the fifth joint.) 



Phassus, n.^ 

 Type P. columbianus, n.^ 



2. Upper margins of the fifth caudal joint rounded, not forming 



an elevated keel Isometrus, (Hempr. et Ehr.), 1829. 



Type /. maeulatus, (DeGeer), 1778*, 



plus minus infuscata; segmentis abdomiqalibus costis trinis versus 

 medium, postice, munitis ; cauda gracili, segmentis l''-4'" subcylindratis 

 et carinis inferioribus mediis carentibus, carinis reliquis debilissimis, 

 subtiliter denticulatis ; segmento 5" carinis superioribus carente, salten^ 

 duplo et dimidio longiore quam latiore; vesica sub aculeo mutica; 

 digito mauus mobili manu postica non vel vix longiore, ordinibus 

 dentium secundum mediam aciem ejus 9; dentibus pectinum 29-31. 

 Long, circa 47 milHm. Africa, Cafiraria. 



^ Nom. propr. mythol. 



^ Phassus columbianus, n. 



Oephalothorace sat crasse granuloso, nigro et fusco-testaceo variato, 

 abdomine nigricante, ordinibus 5 longitudinalibus macularum fusco- 

 testacearum; cauda basi fuso-testacea, apice late nigricante, ibique sat 

 fortiter angustata, vesica parva, oblonga, crasse granulosa, sub aculeo 

 dente forti compresso supra bidenticulato armata; manibus brachia 

 latitudiue fere sequantibus, evidentissime granuloso-costatis ; digito 

 manus mobili manu postica duplo longiore, ordinibus denticvdorum 

 secundum mediam aciem ejus circa 8 ; dentibus pectinum fere 12. 

 Long, circa 32 millim. America merid., Columbia. 



3 = Scorpio americns, Linn., 1758. I suppose we cannot well retain the 

 Linneau name of this scorpion, as Linngeus had already in 1754 (in his 

 ' Museum Adolphi Friderici,' where the binominal nomenclature is con- 

 sistently and constantly employed) given the name S. americanus to another 

 species of Isometrus. In his ' Syst. Nat.' ed. 10 (1758) and in ' Mus. 

 Ludov. Ulricse ' (1764), Linnaeus changed the name of that scorpion, er- 

 roneously considering it identical with a European species, into S. europceus, 

 although the specimen which he had described was from America. This 

 S. americanus, Linn. 1754, or S. europceiis, ejusd. 1758, in which, according 

 to Linnaeus (Mus. Ludov. Llricse, p. 429), the hands are " supra angulatse, 

 admodum (tnffusta^," is no doubt identical with <S'. europaeus, DeGeer (of 

 which I have seen the type specimen), or S. obscwKS, Gerv., which species 

 I therefore call Isometrus americanus, (Linn.). 



