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BIBLIOGRAPHY OF PALASOZOIG CRUSTACEA 119 
WALCOTT (Charles D.)—Continued 
Albertella n. genus, Genotype 4. Helena n. sp. 
The genus should be compared with the genus Zacanthoides. ‘Che cephalons of the 
two genera are generically the same. ‘The thoracic segments are the same type, but the 
third or fourth segment of the thorax of Albertella is extended into long pleural spines, 
and the thorax has seven instead of nine segments as in Zacanthoides. The pygidium 
has one pair of spines instead of many spines, as in Zacanthoides. 
Albertella Bosworthi n. sp. 
Oryctocare new genus, genotype O, Geikiei n. sp. 
The cranidium of the cephalon of this genus is much like that of Oryctocephalus, 
but the thorax and pygidium are unlike. ‘Phe pleurae are of the Olenus type, while 
the pygidium is broad and of the Bathyuriscus type. 
= 
Zacanthoides idahoensis n, sp. Neolenus inflatus n. sp., intermedius n. spy N. 
intermedius pugio n. variety, M. superbus n. sp. 
Bathyuriscus ornatus n. sp. 
- Middle Cambrian Merostomata. 
Smithsonian Mis. Coll. vol. 57, No. 2, Washington, 1911. 
In this paper two genera, Sidneyia and Amiella, are described. 
Sidneyia inexpectans Wale. Amiella ornata Walc. Neolenus serratus Rominger. 
Beltins Danai Wale. 
The new genera are placed in a new sub-order Limulava of the order Eurypterida. 
Sidneyia with its four pairs of cephalo-thoracie appendages and simple antennae 
approaches the ‘lrilobita, which has a similar scheme of cephalic appendages. 
——— Cambrian Geology and Paleontology, No. 6. Olenellus and 
other genera of the Mesonacidx. 
Smithsonian Misc. Collections, vol. 53, No. 6, 1910, pp. 231-422, Pls. 22. 
The author under the family Mesonacidae places: 
1. Nevadia n. gen. genotype N. Wetksi n. sp. 
In the type of this genus the posterior 11 segments have only the axial lobe and a 
spinose continuation on each side. ‘The spinose extensions of the posterior segments 
are proportionally much rounder and smaller than those of the anterior 17 segments. 
The pygidium is small without pleural lobes and transverse furrows. 
2. Mesonacis: ‘This form is essentially the same as Elliptocephala, but it has an 
enlarged third segment in the adult, and a strong spine on the fifteenth segment. 
The species referred to Mesonacis are M. vermontana Hall, M. Mickqwitzi Schmidt, 
and M, Torrelli Moberg. 
Elliptocephala [Emmons 
genotype EF. asaphoides Emmons. 
In the genus the posterior five segments are more highly developed than the primi- 
tive segments of Nevadia, but not as much so as the segments anterior to them. 
Callavia Matthew, genotype Olenellus (Holmia) broggeri Walcott. 
This genus was proposed by Matthew, Am. Geol. vol. 19, p. 397, 1897, for O. 
broggeri and O. callavii Lapw., on acccount of the glabella differing from that of 
Olenellus (Holmia) Kjerulf. 
Callavia has a trace of the constricted pleurae of the posterior portion of the thorax in 
the two last segments. The broad thorax of Callavia with the falcate extensions of 
the pleurae are unlike the narrow thorax of Holmia, with its spinos pleural extensions. 
The glabella of Callavia is narrower and more primitive, and its intergenal spine is 
less primitive. The pleural furrow of Callavia is narrow and oblique, like that of 
Paradoxides, while the pleural furrow of Holmia and Wanneria is broad and straight. 
The segments of Callavia appear to be nearer to Elliptocephala, than to those of 
Holmia. 
