234 HISTERIDA. 
striato; mesosterno antice semicirculari, angustissime marginato; antennis pedibusque rufis; tibiis anticis 
7-, intermediis 5-spinosis. Long. vix 2 millim. 
Hab. Guatemata, Aceytuno (Champion). 
One specimen. This very remarkable species has the pygidium produced into a 
cone in the middle, from which point it is convex above and deeply concave or scooped 
out beneath. The structure of the pygidium somewhat approaches the form familiar 
to us in Trypaneus, with which Teretriosoma and Teretrius should doubtless be 
associated, although Marseul (Ann. Soc. Ent. Belg. xiii. 1870, pp. 61, 120) places 
Trypaneus between Lioderma and Apobletes, and Teretrius after Saprinus. 
5. Teretriosoma cavifrons, sp.n. (Tab. VII. figg. 3, 3a, 0.) 
‘Cylindricum, subelongatum, eneo-brunneum, nitidum; antennis pedibusque rufis; fronte grosse punctata, 
inter oculos prominula, in medio transversim sulcata, antice late et profunde excavata; pronoto antice 
minute, postice grosse, punctato, stria integra valida; elytris haud striatis; propygidio subocellato- 
punctato; prosterno haud striato, grosse et sparse punctato; mesosterno immarginato, a metasterno haud 
distincto; tibiis anticis extus 7-, intermediis 8-, posticis 5-dentatis. Long. 21 millim. 
Hab. Mexico, Colima city (Hége). 
One example. This species shows in a very remarkable way the modifications 
to which the genus Teretriosoma is liable. Dr. Horn has remarked that the genus is 
intermediate between Teretrius and Xiphonotus, and in the present species there is on 
the forehead a similar projection to that on the thorax of Xiphonotus chevrolati, Mars. 
In some respects the frontal structure resembles that of a species of Cis. The thorax 
is punctured very much as in 7. virens, the punctures being fine anteriorly, and gradually 
increasing in size towards the base. 
6. Teretriosoma paradoxum, sp.n. (Tab. VII. figg. 4, 4a.) 
‘Cylindricum, eneum, metallicum, undique sat dense et fortiter punctulatum ; antennis pedibusque rufis ; fronte 
convexa, parum transversa; pronoto stria laterali sinuata, antice late interrupta, in medio fortiter tuber- 
culato; pygidio grosse punctato, apice leviter impresso; prosterno robusto, prominulo, minutissime 
strigoso, truncato, antice parum concavo, haud striato; mesosterno antice acuminato, stria subintegra; 
pedibus anticis et intermediis 6-dentatis, posticis 3- vel 4-spinosis, Long. 23 millim. 
Hab. Mexico, Guanajuato (Sal/é). One example. 
This singular species is placed in Teretriosoma, owing to its colour and to the 
‘pygidium showing a slight tendency towards concavity at its apex. In general outline 
it corresponds with several species of Cis. The tubercle on the thorax is a very 
prominent specific character, and is unlike that of any other described Histerid. In 
Xtphonotus the thorax is produced in front on the same plane as the head, but in the 
present insect the thoracic tubercle is subvertical. The prosternum is very large, and 
anteriorly very prominent, with the apex somewhat abruptly concave. The marginal 
stria of the mesosternum is not very distinct, and is not apparently complete in front. 
