TRENTON LIMESTONE. 
245 
302. 3. CERAURUS VIGILANS. 
Pl,. LXV. Figs. 2 a-h. 
Compare Entomolitlius, No. 2, Linne, Vet. Acad. Handlingar, 1759, T. 1, fig. 2. 
Entomostracites punctatus (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, Schlotheim, Nachtrage, 1823, Vol. ii, pag. 37, no. 23. 
Calymene punctata, Dalman, Vet. Acad. Handlingar, 1826, pag. 233 & 267, pl. 2, fig. 2 a b. 
— — Hisunger, Letb. Suecica, 1837, pag. 12, pl. 1, fig. 6. 
— ? ? — Murchison, Sil. System, 1839, pag. 661, pl. 23, fig. Sab. 
Jlmphion multisegmetitatus, Portlock, Geol. Rep. Londonderry, 1843, pag. 291, pl. 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; pleurai much extended; caudal shield elongated, the lateral 
lobes with nine simple segments, while the central lobe has twice as many; every second 
segment of the central lobe of the thorax is marked 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.* 
*1 have a specimen from Dudley, in England, marked Calymene punctata, in which there are two caudal shields. 
