Geology . Fig. 360.—Jurassic Ccelexterata and Echintodermata: a, b, Thamnastrcea pro-lifera Becker, a complete corallum, and the lateral surface of a costal septumenlarged; c, Thecosmilia trichotoma (Goldf.); d, Pentacrinus bnareus Mill; e,Cidaris coronata Goldf. majority of the Jurassic crinoids were undoubtedly shallow-waterforms, as most of the Paleozoic types had been; but there is evidence THE JURASSIC PERIOD. 85 that deep-water species had begun to appear, leading toward the presentdominant but not exclusive habit. (5) The long, slow evolution of the echinoids in the Paleozoic erawas suc

---

Geology . Fig. 360.—Jurassic Ccelexterata and Echintodermata: a, b, Thamnastrcea pro-lifera Becker, a complete corallum, and the lateral surface of a costal septumenlarged; c, Thecosmilia trichotoma (Goldf.); d, Pentacrinus bnareus Mill; e,Cidaris coronata Goldf. majority of the Jurassic crinoids were undoubtedly shallow-waterforms, as most of the Paleozoic types had been; but there is evidence THE JURASSIC PERIOD. 85 that deep-water species had begun to appear, leading toward the presentdominant but not exclusive habit. (5) The long, slow evolution of the echinoids in the Paleozoic erawas succeeded in the late Trias by the beginning of a rapid and strongevolution in the form of sea-urchins, and these were now on theirrapidly ascending curve which reached its climax in the early Jura was especially rich in the so-called regular sea-urchins(Cidaroida and Diadematoida). The cidarid type, with large club-shaped spines, was characteristic (Fig. 360, e). (6) The crustacean dynasties o

---

Size: 2011px × 1242px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No

Keywords: ., bookcentury1900, bookdecade1900, bookpublishe, booksubjectgeology