1870.] GEOLOGY AND MINERALOGY. 223 



ill this specimen, furnisli a specific mark. Amongst other frag- 

 ments from this bed, which Dr. Dawson has submitted to me, is a 

 small piece of tubercle ornament, possibly belonging to the same 

 species of CepJialaspis. In this, the tubercles are very sharply 

 moulded and nearly hemispherical. Various other fragments 

 which cannot be identified, but are probably bits of fish bones, 

 etc., are amongst the collection. 



A very fine fish-spine — the Machairacanthus sulcafus — was also 

 obtained in the sandstones associated with the shale which furnished 

 the CepJialaspis. This sandstone is not unlike the sandstone of 

 Glamis, and other parts of Perthshire and Forfarshire which 

 furnish CepJialaspis ; whilst the shale strongly recalls the Forfar- 

 shire shale, which has furnished Mr. Powrie with his beautiful 

 CepJialasjyis Pagei. 



The spines which occur in the Cornstones of Herefordshire, 

 which have not yet been worked out, are of various forms and are 

 usually "lumped" as OncJiiis. None, however, appear to resem- 

 ble 3IacJiairacantJius, with its remarkable keeling like the petiole 

 of a s^veet-pea, I propose to call the new American CepJialaspis 

 after the illjstrious geologist who has allowed it to be figured 

 here : CepJialaspis Dawsoni. 



Embryology of Limulus. — Dr. Packard has presented to 

 the American Association a very interesting account of the early 

 stages of the development of the Limulus p)oli/pJiemus of the 

 iVmerican coast. In one of its earlier stages it bears a remarkable 

 resemblance to such Trilobites as Trinucleiis. In a subsequent 

 stage the abdominal segments became consolidated, and it re- 

 sembles not the adult but the larva of Trinucleiis. The develop- 

 ment in these two groups is thus in opposite directions — tli:it of 

 Limulus tendino; to the consolidation of the abdominal ses-ments, 



O O 7 



that of Trilobites to the addition of new se2;ments between the 

 original head (cephalothorax ?) and abdomen. In this way Dr. 

 Packard's facts raise new questions as to the grade and affinities 

 of Trilobites, especially when taken in connection with Mr. 

 Billings' observations as to their feet. The alliance between the 

 two forms is evidently very close. Dr. Packard thus sums up his 

 conclusions : — 



Conclusions. — The eggs are laid in great numbers loo.se in the 

 sand, the male fertilizing them after they are dropped. This is 

 an exception to the usual mode of oviposition in Crustacea ; 



