376 Reviews — Novitates Palcvozoicce. 



which Barrande called Anatifopsis, and their study leads him to 

 conclude that the geuus should be placed in the Lepidocoleidse. His 

 description and figures are, however, far from convincing. For one 

 thing, the ornament of his fossils differs in several respects from the 

 growth-lines of both Anatifopsis and Lepidocoleas. 



The description of some new Eurypterid remains leads 

 Dr. Ruedemann to traverse the view of A. W. Grabau and 

 Miss M. O'Connell that the Eurypterids always lived in rivers, and 

 this he does to good effect. 



The existence of eyes in the limuloid arachnid Pseudoniscus, of 

 Silurian age, has long been debated. Specimens of two species here 

 described show small but distinct eyes on the facial suture further 

 forward than they had been alleged to occur in the known species 

 from Oesel. Somewhat similar reduced eyes in the trilobites have 

 occasionally been called " ocelli ", but no eyes truly homologous with 

 the ocelli or median eyes of Merostomata and of various Crustacea 

 have hitherto been demonstrated. Both Beecher and Cowper Reed, 

 however, have suggested that the distinct and isolated tubercle on 

 the median line of the glabella in Trinucleus may be such a median 

 eye. Dr. Ruedemann now maintains the correctness of that 

 suggestion, and extends it to most, if not all, trilobites, for the 

 following reasons. Such a tubercle is found in many species 

 belonging to over thirty genera, and its frequent association with 

 a smooth glabella proves that it had some use. In T. tesselatus, 

 of which he gives good figures, and in other species, he has found 

 evidence of a lens, not crystalline, but probably a sack filled with 

 fluid. The test is thinner over the tubercle. The tubercle is more 

 prominent in early growth-stages, as are true ocelli, and is well 

 developed when the lateral eyes are aborted. It is always on the 

 highest point of the glabella, generally between the lateral eyes, and 

 often at the hinder end of a short crest which may indicate the course 

 of the nerve. An ocellar tubercle or mound is commonest in 

 Ordovician and Silurian trilobites. In Cambrian genera there is 

 some evidence of transparent spots. In Devonian genera the strong 

 development of the lateral eyes may have led to the loss of the median 

 eye. The occurrence of a median eye in many primitive arthropods 

 renders it a priori probable that such an organ was also possessed by 

 the trilobites. 



The discovery of a median eye in Trinucleus showed that the 

 vestigial eyes of that genus were not ocelli but lateral eyes, and 

 suggested search for the sutures on which they should occur. The 

 detection of these here and elsewhere corroborates the views of 

 Jaekel, Richter, and Swinnerton (Geol. Mag., 1915, p. 490) and 

 upsets the Order Hypoparia. The search also led to the discovery of 

 a new suture, which starts from a minute tubercle at the front end 

 of the short crest mentioned above, and diverges to enclose the middle 

 region of the front end of the glabella. Dr. Ruedemann suggests 

 that this is "the rostral piece or epistoma . . . drawn up into the 

 glabella by the exceptional swelling of the frontal lobe of the glabella 

 and the development of the broad brim ". 



Enough has now been said to show how the palaeontologists of 



