TRENTON LIMESTONE. * 245 



302. 3. CERAURUS VIGILANS. 



Pl. LXV. Figs. 2a-h. 

 Compare EntamolUkus, No. 2, Linne, Vet. Acad. Handlingar, 1759, T. 1, fig. 2. 



Entomostracites punctatua {Trilobus punctatus, Brunn.), Wahlenberg, Act. Soc. Sc. Upsaliensis, 



1821, Vol. viii, pag. 32, no. 7, tab. 2, fig. 1. 

 — — Brongniart, Crust, fossiles, 1822, pag. 36, tab. 3, fig. 4. 



Trilobites punctatus, Schix)theim, Nachtrage, 1823, Vol. ii, pag. 37, no. 23. 

 Calymene punctata, Dalman, Vet. Acad. Handlingar, 1826, pag. 233 & 267, pi. 2, fig. 2 a b. 



— — HisiNGER, Leth. Suecica, 1837, pag. 12, pi. 1, fig. 6. 



— ? .' — M0RCHISON, Sil. System, 1839, pag. 661, pi. 23, fig. Sab. 

 Amphion multisegmentatus, Portix>ck, Geol. Rep. Londonderry, 1843, pag. 291, pi. 3, fig. 6. 



Buckler subcrescent-form, with the posterior angles extended into long sharp spines, 

 which, when perfect, reach backward to the commencement of the caudal shield ; entire 

 surface of the buckler studded with strong tubercles ; glabella not lobed, front margin 

 thickened and studded by two lines of tubercles ; oculiform tubercles subconical, remark- 

 ably prominent, granulated ; facial suture as in the preceding species ; maxillary shield 

 thickened and tuberculated at the margin ; labrum small, ovate, attached directly to the 

 front of the glabella ; thorax with eleven articulations, the lateral lobes three times the 

 width of the central lobe ; pleurae much extended ; caudal shield elongated, the lateral 

 lobes with nine simple segments, while the central lobe has twice as njany ; every second 

 segment of the central lobe of the thorax is^arked by a tubercle or short spine, and every 

 third (or fourth) segment of the central lobe of the caudal shield ; alternate segments of 

 the lateral lobes more or less distinctly tuberculated. 



In all the specimens which I have seen, the body is partially contracted, and the lateral 

 articulations bent downwards so that their terminations cannot be seen ; it is not improbable 

 that some of them terminated in spinous processes, as in the preceding species. The posterior 

 angles of the buckler, when perfect, terminate in long spines, which extend to the caudal 

 shield, and are curved upwards at the extremity ; but these are frequently broken off, and 

 the species might readily be mistaken. Surface of the buckler marked by pustular tubercles. 

 The articulations are granulated, and every second one of the axial lobe of the thorax has 

 a prominent tubercle or short spine, which is not often seen, however. The caudal shield 

 closely resembles the figures cited above, though the glabella given by Wahlenberg as of 

 the same species is totally different from our species, and probably not belonging to the 

 caudal shield there figured. The great disproportion in the number of articulations of the 

 middle and lateral lobes of the pygidium is very remarkable ; every third articulation in 

 the central lobe is furnished with a short spine, which is usually broken off in all the 

 specimens yet seen. 



Nearly all the specimens are distorted by being bent downwards just behind the buckler, 

 while the latter is elevated and thrown somewhat backwards, giving it a remarkably 

 prominent appearance.* 



• I have a specimen from Dudley, in England, marked Calymene punctata, in which there are two caudal shields. 



