436 H. Woodtvard — Notes on Talmozoic Crustacea. 



Oesel, namely, Pseudoniscus acnleatus (Woodcut, Fig. 2), and 

 Exajmitirus SchrenTcii (Woodcut, Fig. 3) ; and Prof. Eicliwald has 

 described a third form under the name of Bunodes lunula (Woodcut, 

 Fig. 4) from the same rich locality and formation.' 



Fig. 2. Fig. 3. Fig. 4. 



Fig. 2: — Pseudoniscus acnleatus, Nieszk. \ 



Fig. Z.—Exapijiurus Schrenkii, Nieszk. > All from the U. Silurian I. of Oesel, Baltic. 



Fig. 'i.— Bunodes lunula,^ Eichw. ) 



All these forms show three well-marked divisions to their bodies, 

 namely, head, thorax, and abdomen, and all (save Bunodes) possessed 

 a telson, or tail-spine, and free articulated thracio somites. 



In addition to Hemiaspis limuloides, already described, there are 

 certain other specimens in the Museum of Practical Geology, to 

 which Mr. Salter has appended MS. names, namely — 

 Hemiaspis (Limuloides) speratus, Salter, MS. 

 „ „ optatus, „ 



„ „ tuherculatus, „ 



In Lowry's chart of the genera of Fossil Crustacea designed by 

 Mr. J. W. Salter and myself, Mr. Salter has figured a head- shield of 

 Hemiaspis under the name of H. Salweyi. There can be no doubt 

 that this form is identical with Limuloides tuherculatus of Salter. I 

 consider his Limuloides speratus and L. optatus to represent but one 

 species, closely allied to H. limuloides. A portion of the head-shield 

 of another form distinct from the foregoing, from the Wenlock shale, 

 Dudley, completes the known species of Hemiaspis. 



Species 2. — Hemiaspis speratus, Salter, MS. sp., Plate X. Figs. 

 5 and 7. 



This species is represented by four head-shields only; the 

 body-segments are not known. Limuloides optatus, Salter, MS., is 

 not specifically distinct from L. speratus of Salter, and is conse- 

 quently not retained. 



It is no doubt closely related to H. limuloides already described, 

 but the carapace is broader in proportion to its length, and the 

 radiating lines or ridges which in that species take their rise around 



1 ' Archiv fiir die Naturk. Livonia, Esthonia, und Kurlands,' erste serie, zweiter 

 bd., tab. ii figs. 12, 13, and 15, pp. 378-382. (Dorpat, 1859.) 8vo. 



2 It is just possible that Bunodes may prove to be an Arachnid related to Scudder's 

 Architarbus rolimdatus from Illinois, U.S., and A. subovalis, H. Woodward (see 

 Geol. Mag., 1872, Vol. IX., September number, p. 385, PI. IX. Figs. 1 and 2). 



