ARACHNIDA— XIPHOSURA 



775 



called the Trilobite stage (Fig. 1500, B). After the first moult the caudal spine begins to 

 elongate, and at this stage, while the abdomen retains its segmented larval character, a true 

 affinity with tlie Paleozoic Prestwichia and Beiinurus is clearly revealed. The prevailing 

 modern view is that in Lirmihis we have a meniber of the Arachnida which retains its water- 

 breathing liabit, and, in the features of the abdominal appendages, some traces of the 

 characteristic structure of the primitive crustacean stock from which the Arachnida originally 

 sprang. 



The genus first makes its appearance in the Trias, one small species being known from 

 tlie Buntersandstein of the Vosges, and another, L. vicensis Bleicher, from the Keuper of 



B, Embryo ot Limulus, 

 in the so-ctiUed "Trilo- 

 bite stage." Lateral 

 eyes faintly shown. 

 (After Dohrn.) 



C, Limulus priscus 

 Münst. Muschelkalk ; 

 Laineck, near Bay- 

 reuth, i/i- 



Fui. 1500. 



A, Liimilus walchi Desm. Lithographie Stone ; Solenhofen, Bavaria. Dorsal and ventral aspeets, the 

 latter showing several pairs of imperfectly preserved ambulatory limbs. On the.carapace, covering the prosoma, 

 are seen impressions of the lateral eyes. 



Lorraine. L. walchi in abundant in the Lithographie Stone of Bavaria ; L. natkorsH and 

 L. woodivardi are Jurassic species from Sweden and England respectively ; L. syriacus 

 occurs in the Cretaceous of the Lebanon ; and L. decheni occurs in the Oligocene brown coal 

 of Teuchern, near Merseburg.^ 



Order 2. SYNXIPHOSURA Packard. 



Body elongated ; cephalothorax semicircular with more or less distindly defined 

 median axis, and no facial sntures. Compound eyes generally present, ocelli not 



^ Böhm, J., Über Limidus decheni Zincken. Jahrb. Preuss. Landesanst. Bergakad., 1905, 

 xxvi. Oiie of these specimens described by Böhm represents doubtless the largest known 



vol 

 Limidus 



