a4 SAN DIEGO SOCIETY OF NATURAL HISTORY 
LINDSTROM (G.)—-Continued 
scarbridus Ang., S. latifrons Ang., 8. lacinatus nov., 8. Beyrichi nov. Youngia new 
genus genotype Cheirurus trispinous Etheridge and Nicholson. 
Cephalon semi-circular with long spines to the genal angles; glabella sub-circular 
convex truncated posteriorly by occipital furrow overhanging front 3 pairs of lateral 
furrows to the glabella; occipital ring with long spine; fixed cheeks, small, short, nar- 
row. Pygidium not known. 
The author describes as new Youngia globiceps and Y. inermis Deiphon Forbesi 
Barr. Encrinurus punctatus Wahlen., E. laevis Ang. E. obtusus Ang. Acidaspis 
crenata Emm., A. Barrandei Ang., A. Marklini Ang., A. pectinata Ang., A. (Trapelo- 
cera) bicuspis Anglin. Lichas concinnus Ang., L. latifrons Ang., L. palifer nov., L. 
araneus nov., L. ornatus, L. marginatus nov., L. visbyensis nov., L. plicatus nov., L. 
triquetrus noy., L, rotundifrons Ang., L. gotlandicus Ang. Trochurus Salteri Fletcher. 
The generic name of ‘Trochurus was used by Beyrich Bohm, ‘Tril., 1845, p. 31, for 
a composite and artificial species consisting of the head of Staurocephalus Murchisoni 
and the tail of Lichas palmata Barr., which the author recognized in the Untersuch 
uber Tril., 1846, p. 10, and declared that the genus did not exist. ‘he name was re- 
vived by Lindstrém in a wider and slightly different sense, giving Lichas Salteri as 
the type, including Trochurus pusillus Ang. Harpes acuminatus nov. 
Calymmene tuberculata Brunnich, C. spectablis Ang. C. laevis nov., preoccupied 
by Munster of a species of Calymmene which is now referred to Phacops (C. Lind- 
stromi noy.) Calymmene frontosa nov., C. intermedia nov., C. excavata nov. C. papil- 
lata nov. Homalonotus Knighti Konig. Phaetonides Stokesi Murch., P. rugulosus 
noy., P..longifrons nov. Cyphaspis elegantula Ang. C. punctillosa nov. Proetus con- 
cinnus Dalm., P. obconicus noy., P. distans nov., P. acutus nov., P. conspersus Ang., 
P. signatus noy., P. granulatus novy., P. 
verrucosus noy. Illaenus subgen. Bumastus 
barriensis Murch., B. Holmi nov., B. sulcatus nov. for Illaenus insignis Holm. Bronteus 
platyactin Ang., B. Marklini Ang., B. polyactin Ang., B. irrandians nov., B. umbonatus 
nov., B. crebristriatus nov. 
Merostomer: Eurypterus Fischert Eichw. Pterygotus osiliensis Schm. 
— Ueber die Schichtenfolge des Silur des Insel Gotland. 
Neues Jahrb. Min. Geol. Pal., Bd. 1, 1888, pp. 147-164. 
——— Researches on the visual organs of the Trilobites. 
Kongl. Svenska Vetenskaps Akad. Handlingar Bandet 34, No. 8, 1901. 
Dr. Lindstrom considers certain nodes on the hypostoma to be visual organs. ‘This 
is based on the discovery of Dr, Liljevall from the hypostoma of Bronteus polyactin 
Ang. ‘They are located on the inferior edge of the upper groove, close to the lateral 
margins. ‘To these tubercles he gives ‘the name of “maculae”. ‘hey are oblong or 
ellipsoid; their inferior apices bluntly pointed or rounded, two-thirds of their surface 
is perfectly smooth or glossy, and the lower one-third covered with a compact accumu- 
lation of small granules, similar to the facets of the compound eyes of ‘Trilobites. ‘The 
author, therefore, assumes that they are a pair of small adventive eyes on the exterior 
side of the hypostoma, from the perfect structural agreement between them and _ the 
eyes of the head. ‘The author sums up the literature on blind trilobites without facial 
ridge; also those with facial ridge, and illustrates the maculae on the hypostoma of 
39 genera and 136 species. 
The different genera are divided into six groups as follows: 
Group 1—In the sectioned maculae there is no tract of any structure. ‘The test of 
the maculae considerably thinner than that of the hypostoma. According to the affinites 
of the genera they may be subdivided as follows. a—Bumastus, Dysplanus. b— 
