ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 277 



and consisted of a chimney, a narrow passage, and a basal expanded 

 chamber, but the author believes that the chimney is due only to tho 

 mud thrown out in excavating, and has no special significance. After 

 being made, the burrows are sealed with mud for some distance from the 

 top. 



Palaearctic Isopods.* — Prof. Karl W. Verhoeff continues his notes on 

 this subject. In the present instalment he gives a key to the species of 

 the imperfectly known genus Trichoniscus, and describes some new 

 species. 



Professor Verhoeff further discusses Armadillidium, Porcellio, and 

 some other related genera. In regard to distribution, he notes that 

 north and central Europe are poor in land Isopods, those present are 

 widely distributed forms, and there are few or no characteristic species. 

 On the other hand, the Mediterranean sub-region is rich in land Isopods, 

 as it is also in Chilopoda and Diplopoda. 



New Entozoic Copepod.f — Alice L. Embleton describes Goidelia 

 japonica g. et sp. n., from the rectum of Echiurus unicinctus, an almost 

 unknown Japanese Gephyrean. The parasites most resemble the Hersi- 

 liidae (for which and for Hersilia, it seems necessary to substitute the 

 names Clausidiidas and Clausidium). The body is flattened, segmented, 

 and cyclopoid ; the sexes are equal in size, and dimorphism is only 

 apparent on closer examination of the appendages ; the male is not at- 

 tached to the female ; there are no eyes. Along with the Copepods 

 there were very numerous specimens of a minute Infusorian, apparently 

 a new species of Trichodina. 



Alleged Hypostomial Eyes in Trilobites.J — G. Lindstrom, with the 

 assistance of G. Liljevall, has investigated the visual organs of the 

 Trilobites. There are four types of cephalic eye, which the authors 

 believe to have succeeded one another in the following order, viz. : — the 

 simplest or Harpes type, of simple ocelli ; the Eurycarid, biconvex or 

 lentiform type ; the Megalaspid or prismatic type • and the Phacopsid 

 or " aggregate " type — all duly figured for thirty-six species. 



Apart from these, the authors record " maculae " or hypostomial eyes 

 so-called for some 136 species of 39 genera, but they state that the 

 genera in which they have found them lens-bearing are relatively few, 

 and that the lenses or " granules," even where recognisable, have been 

 found to be present only over the lower third of the macula, with the 

 exception of the Asaphidaa, Illsenus, and LicJias, where the entire macula 

 shows the structure which characterises it as a visual organ. Beyond 

 this, the macula, for which an average diameter of 0*99 mm. is given, 

 is described as oblong or ellipsoidal anchor two-thirds of its surface 

 perfectly smooth or rather glossy, and its granules or lenses are esti- 

 mated to be but 0*055 mm. in diameter at their largest. 



The presumed hypostomial eyes are compared with a thin area of 

 the hypostome of Apus, with the (according to Packard) originally 

 ventral median eyes of Limulus, and with more or less ventral eyes in 

 Lepadidae. Perhaps, like the living Apus, the Trilobites were in the 



* Zool. Anzeig., xxiv. (1901) pp. 73-9, 135-49 (4 figs.)- Cf. this Journal, ante, 

 p. 154. f Journ. Linn. Soc. (Zool.), xxviii. (1901) pp. 211-29 (2 pis.). 



X Handl. k. svensk. Akad. Stockholm, 1901, 74 pp., 6 pis. 



June 19th, 1901 u 



