258 The American Geologist. ^p"""- ^'-^oi. 
Researches on the I'isual Organs of the Trilobitcs. By G. Li.n'dstkom. 
Six Plates. (Kongl. Svenska Vetcnskaps Akad. Handl., Bd. 34. 
No. 8.) 
This is a most important contribution to the biology of the trilobites. 
First, because it challenges proof of the presence of eyes in many spe- 
cies that are supposed to have had visual organs, denying that the struc- 
tures that have been taken as such are eyes. And secondly because it 
announces the discovery of true ej'es on the hypostonse of many spe- 
cies. 
Lindstrom claims that the assumption that because a trilobite had 
an "eye lobe" it therefore had eyes is quite without foundation, for he 
teaches that this "eye lobe" is due to the impact of the free-cheek at 
this point with the inner cheek, and he states that in a number of spe- 
cies which he has examined there is no space for an eye between the 
two pieces of the head shield which there come in contact. The oldest 
genera with true eyes on the cephalic shield, which he recognizes, are 
such of the Upper Cambrian, as Petiera Sphoerophthalmus and Ctino- 
pyge. In the Ordovician, Silurian and Devonian, the genera in which 
true eyes exist on the head shield, are multiplied. There is an interest- 
ing discussion on the origin of the facial suture with applications in 
Olenellus, Paradoxides, Liostraeus, Solmopleura, etc. He does not rec- 
ognize the presence of eyes or a suture in Agnostus. 
Most interesting to palaeontologists is the announcement that the tu- 
bercles or, as Mr. Lindstrom calls them, the "maculae" in the anterior 
furrow of the hypostome, as seen in many species, had ocular proper- 
ties. Not onljr by the thinness of the skin over these spots, but by the 
actual presence of lenses in them, has he proved that the maculae in 
many species possess this office. This discovery of this condition of 
the maculae was made by his draftsman and assistant, Herr G. Lilje- 
vall. Many trilobites, it would thus appear, had eyes below as well 
as on the upper side of the headshield. 
This important memoir is fully illustrated with six admirable plates 
and several text figures ; in the former the admirable handiwork of 
Herr Liljevall is patent. 
That this work is foimded on abundant material niaj^ be assumed 
when it is stated the hypostomes of thirty-six species of trilobites have 
been sectioned for investigation. These range from the Cambrian to 
the Devonian. 
Herr Lindstrom considers that the trilobite eye is best represented 
in that of Apus and the Isopod. g. f. m. 
CORRESPONDENCE. 
On the Age of Certain- Gr.anites in the Kl.^m.^th Mount.mn.s. 
[Abstract.] Small batholyths and dikes of granite, quartz-mica-dioryte 
and intermediate types are shown to occur at various places in the 
Klamath region, but in areas quite subordinate in extent to those of 
the metamorphic rocks in which they have been intruded. The same 
