. Cephalopoda. Cephalopoda. These changes lead to the recent types of Teuthoidea, i. e. the Meta- teuthoidea. The fossil forms from which the Metateuthoidea can be derived (p. 47) are named Mesoteuthoidea. Mesoteuthoidea (=Loliginites crassicarinati Quenstedt) Diagnosis: Fossil Teuthoidea (Liassic to Cretaceous) with the median plate of the proostracum tapering anteriorly into an arc, apex or pointed process and bent more or less distinctly into a groove (keel) which is open ventrally, and not delimited sharply by asymptotes between the median plate and the lateral plates. Cone flag large, occ
. Cephalopoda. Cephalopoda. These changes lead to the recent types of Teuthoidea, i. e. the Meta- teuthoidea. The fossil forms from which the Metateuthoidea can be derived (p. 47) are named Mesoteuthoidea. Mesoteuthoidea (=Loliginites crassicarinati Quenstedt) Diagnosis: Fossil Teuthoidea (Liassic to Cretaceous) with the median plate of the proostracum tapering anteriorly into an arc, apex or pointed process and bent more or less distinctly into a groove (keel) which is open ventrally, and not delimited sharply by asymptotes between the median plate and the lateral plates. Cone flag large, occupying about half the length of the gladius and passing posteriorly into the spoon- or scoop-shaped cone. Outer asymptotes marked clearly but not sharply by a slight bend of the growth lines. Four families (p. 47) are listed below. 1. Trachyteuthidae. Plump Teuthoidea with Sepia-like shell, which is strongly calcified, with a zone of tubercles along the middle of the dorsal side. Median plate of proostracum still relatively wide, ending anteriorly in a rather blunt arc (Figure 62, Chapter 4), without distinct keel. (Tra- chyteuthis hastiformis Riipp. from the Solnhofen slates, and related species. (Cf. Zittel-Broili, 1915, p. 582, Figure 1, 273.) (146. FIGURE 62. Shell ofPalaeololigo Naef= Teuthopsis oblonga Wagner (= T. princeps Wagner), reconstructed after the original i n the Munich paleontological collection and by comparison with well preserved fossils from Solnhofen. Eichstadt and Daiting. Note the spoonlike cone (Co) and the leaflike lateral plates (SpJ which are connected vs'ith the similar halves of the cone flag (Ct) to form the nag-. Ra — free rhachis (the lateral boundary of the median plate is shown) passing into the lateral plates by a longitudinally striped zone (Str); Aa — outer asymptote dividing the proostracum from the cone flag. (This boundary is always distinct also in recent gladii with a well developed flag.) The shell illustrated here is related and
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Keywords: ., bookcentury1900, bookcollectionbiodivers, booksubjectcephalopoda
