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svstfiiialif imporlaiK'i". Bul as llio finger ol' Ideoroncus Idiuinalus n. sp. (PI. 1, 

 ligs. 5 a, b), wliich is one of Hie Hemictenoductijli, l)ears a well developed lamina 

 exterior, this character must at least be modified. 



Serrula interior If we compared the serrula interior of a Cthoniiis CK. 

 with the lamina interior of a Chelifer Geof., we should scarcely find any similarity, 

 but the study of the intermediate forms will connect the extremities in the most 

 l)eautiful manner. This organ is in the Cbthoniidae Hans. f. inst. Ch. terribilis n. sp. 

 (PI. I, fig. 1 c) pointed and only fastened at its base with the two distal thirds free 

 and directed forwards; it is of a slender structure and has its inner margin divided 

 mto a number of more or less obtuse teeth. The serrula is at any rate in some 

 species of the three genera of the Obisiiiiae Dad. broader, has only the terminal 

 portion free and the more or less pointed teeth partly fused ; in Obisiiim imiscoriini 

 Leach, almost all the teeth are pointed and the basal ones are not placed on a 

 level with the others, but directed downwards and forwards (cf. Hansen 49. lab. V, 

 Rg. 9 b). The serrula of the Pseiidobisiinae Hans, has a different structure in the 

 difTerent forms, sometimes pro\iding similarity lo that of the already mentioned 

 subfamilies, and sometimes to that of the Garypidae Hans. The terminal tooth or 

 perhaps more correctly the pointed lip is remarkable in many species like Ideo- 

 roncus laminatus n. sp. (PI. I, fig. 5 a) by being without any apparent connection 

 with the more proximal portion, and by its position on a lower level behind the 

 bases of the preceding teeth; that this independent spine of those forms, in which 

 it occurs, is really the homologous of the terminal spine of other species, may be 

 regarded as probable on account of their similarity and the whole structure of 

 the terminal portion of the serrula, as seen, if comparing the drawings of these 

 organs in Ideoroncus laminatus n. sp. and I. Siamensis n. sp. (PI. I, figs. 4 a and ö a, /). 

 A similar independent terminal spine is observed in the lamina interior of the 

 Garijpidae Hans. cf. p. 20), as well as in the serrula exterior of Garypns irrui/atus 

 Sim. (cf. p. 18). The serrula of Ideoroncus Mexicanus Bks. (21. pi. IX, fig. 2 b) is a 

 slender organ, which has the distal fifth free; the distal teeth are completely free, 

 triangular and serrated along their hindmost margin; the three basal teeth are 

 pointed and free like the distal, and directed obliquely forwards, but the median 

 ones are more or less fused and less pointed; the terminal spine is quite on a 

 level with the proximal portion of the serrula and fused with it. The serrula of 

 Idcobisium Balzanii With (21. pi. X, fig. 2a) and of /. crassimanum Balz, is fused 

 with the fingers in its whole length and has the teeth at least distally triangular 

 and serrated along their hindmost margin (49. tab. V, fig. (5b); the terminal spine 

 is long, slender and moderately curved; it is serrated along the inner margin and 

 placed on a lower level than the preceding teeth. The serrula interior of Ideo- 

 roncus Siamensis n. sp. (PI. I, fig. 4 a, a) bears similarity to that of the previously 

 mentioned forms, but the basal and median teeth are almost completely free and 

 obtuse, while the distal ones are partly free and more pointed; the terminal spine 

 is well developed, on a level with and fused with the preceding portion of the 



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